Fujiko Tsukahara, Yoko Uchida, Ken-ichi Ohba, Akira Ogawa, Toshimasa
Yoshioka and Takamura Muraki
Department of Pharmacology, Tokyo Women's Medical University, School of Medicine, 8-1, Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan
Abstract: Abnormal regulation of mitochondrial uncoupling protein (UCP) gene expression was studied in brown adipose tissue (BAT) of monosodium glutamate (MSG)-induced obese mice. UCP mRNA levels in control mice increased markedly after acute cold exposure; however, MSG-obese mice showed an impaired response. In contrast, an injection of norepinephrine (NE) induced a comparable increase in UCP mRNA levels in control and MSG-obese mice. These results suggest that the impairment in the cold-induced increase in UCP mRNA is due to a deficient sympathetic input to BAT and/or to a diminished response of BAT to endogenous NE, which constitutes the mechanism of impaired thermoregulation in obese mice in a cold environment.
Keywords: Monosodium glutamate, Brown adipose tissue, Uncoupling protein