Adaptive enzyme responses in adipose tissue of obese hyperglycemic mice

Abstract

Effects of fasting-refeeding regimens were studied in genetically obese hyperglycemic mice and their thin littermates to ascertain the possible existence of a differential response. Animals were killed after a 48-hr fast followed by 24, 48, and 72 hr of refeeding with laboratory pellets plus either 15% glucose or 15% glycerol in the drinking water. In addition, obese mice were fasted 96 hr followed by 144 hr of refeeding. In adipose tissue of fasted-refed thin mice, activities of glucose-6-phosphate dehydrogenase (EC 1.1.1.49), malic enzyme (EC 1.1.1.40), alpha-glycerophosphate dehydrogenase (EC 1.1.1.8), lactic dehydrogenase (EC 1.1.1.27), and also glycogen content were increased over control values. In fasted-refed obese mice, neither significant changes in the activities of these enzymes nor glycogen content were observed. In alloxan-treated thin mice, adipose tissue glucose-6-phosphate dehydrogenase activity was decreased, while in identically treated obese animals, only alpha-glycerophosphate dehydrogenase activity was increased. The concept that an impaired “adaptive enzyme” response is a significant aspect of the obese state is suggested by these data.