CLONING OF RAT UNCOUPLING PROTEIN-3 AND UNCOUPLING PROTEIN-2 CDNAS - THEIR GENE-EXPRESSION IN RATS FED HIGH-FAT DIET

In order to elucidate energy balance in the skeletal muscle, we cloned cDNA of a homologue of uncoupling protein (UCP) from rat skeletal mus cle. We also cloned rat UCP-2 cDNA from rat brown adipose tissue (BAT) . The UCP cloned from rat skeletal muscle showed 57% and 72% identity with rat UCP-1 and UCP-2. The mRNA was expressed abundantly in the ske letal muscle, moderately in the BAT, and slightly in the white adipose tissue (WAT) with a major band at 2.5 kb and a minor band at 2.8 kb, while the UCP-2 gene expression was widely detected in the whole body with substantial levels in the WAT and with slight levels in the skele tal muscle and BAT. The rat UCP cloned in the present study showed 86% identity with the recently cloned human UCP-3, which was also express ed abundantly in the skeletal muscle with a signal of 2.4 kb. Therefor e, the rat UCP was considered to be rat UCP-3. In rats fed high-fat di et the UCP-3 gene expression was augmented 2-fold in the skeletal musc le while UCP-2 mRNA levels were increased significantly (1.6-fold) in the epididymal WAT. Augmented expression of UCPs may provide defense a gainst high-fat induced obesity and impairment of glucose metabolism. (C) 1997 Federation of European Biochemical Societies.