Effects of Feeding and Exercise Regimens on Adipose Tissue Glycerokinase Activity and Body Composition of Lean and Obese Mice

Abstract

Glycerokinase activity in adipose tissue has been suggested as the basic genetic difference between lean and obese-hyperglycemic mice. These mice were used as animal models to compare lean and obese adipose tissue glycerokinase activity and to investigate the effects of feed restriction and exercise on glycerokinase activity and body composition. Body weights and feed consumption of ad libitum-fed obese-hyperglycemic mice were significantly higher (P < 0.01) than their lean controls. Liver glycerokinase activity was significantly higher (P < 0.001) than adipose tissue glycerokinase activity in lean and obese female mice. Liver and adipose tissue glycerokinase specific activities were consistently higher in the obese mouse when compared to the lean controls. Obese-hyperglycemic mice pair-weighed to the lean controls and exercised to exhaustion once a day, were approximately the same size but contained more body fat than the lean controls. However, obese mice on the exercise and dietary restriction regimen were less obese than obese mice fed ad libitum. It was concluded: 1) the obese-hyperglycemic mouse is an example of metabolic obesity, but when fed ad libitum the increase in weight over the lean control by a factor of approximately 2.5 is due to a combination of both “metabolic” and “regulatory” factors; 2) adipose tissue glycerokinase activity, which is not significantly higher in obese mice, does not appear to cause the tremendous obesity observed in the obese-hyperglycemic mouse.