Studies on some thermogenetic enzymes in brown adipose tissue of genetically obese mice

The effects of cold exposure on several enzymes in brown adipose tissue (BAT) were examined in two types of genetically obese mice (C57BL/6J-ob and C57BL/6J-Ay) and their thin litter mates. In the thin C57BL/6J mice, the activities of two alpha-glycerophosphate-generating enzymes i.e., glycerokinase (GK) and alpha-glycerophosphate dehydrogenase (GDH), increased in BAT at cold exposure. Resemble results were observed in the yellow obese mice (A(y) mice). Nevertheless, in the obese-hyperglycemic mice (ob mice) showing a poor resistancy to cold, the increases of these enzymes were not observed. In addition, the increase of lipase activity, observed in BAT of the thin litter mates, was also not observed in BAT of ob mice. The decrease of NEFA release from BAT at cold exposure and the prominentry high inhibition rate of lipase by M NaCl were observed also in ob mice. Then the qualitive change of BAT lipase may exist in ob mice.