The Effect of Feed Restriction, Exercise, and Aging on Lipogenesis in Rats

The effect of diet restriction, exercise and aging on body weight, epididymal and perirenal fat pad weights, liver and adipose lipogenesis and lipolysis in male Wistar rats were investigated. The study consisted of four experimental groups: ad libitum fed, sedentary (A) ; diet restricted by feeding on alternate days, sedentary (R) ; ad libitum-fed, exercised by swimming on alternate days (AE) ; diet restricted by feeding on alternate days, exercised by swimming on alternate days (RE) .

Diet restriction as well as exercise resulted in a significantly lower mature body weight, epididymal and perirenal fat pad weights than ad libitum feeding. A significant decrease in these parameters was observed with age.

Hepatic and adipose lipogenesis was estimated by measuring the incorporation of acetate 1-¹⁴C into fatty acids, and activity of glucose-6-phosphate dehydrogenase (G6PD) in vitro. Diet restriction resulted in an increased hepatic G6PD activity (p< 0.005) and adipose tissue fatty acid synthesis (p< 0.01) whereas exercise resulted in increased adipose tissue G6PD activity (p< 0.05) , but it had no affect on lipogenic activity of either tissue. With age, however, fatty acid synthesis and G6PD activity were increased in both tissues.

Hepatic and adipose tissue lipolysis was estimated by measuring the amount of in vitro glycerol release of these tissues. Diet restriction resulted in an increased hepatic and adipose tissue glycerol release, but did not affect adipose glycerol release. The amount of glycerol release of both tissues was increased with age.

In general, neither feed restriction nor exercise improved or prevented age-associated physiological changes. Correlations between physical parameters (body weight and fat pad weights) were significant. Liver fatty acid synthesis and adipose tissue fatty acid synthesis were correlated to both liver G6PD activity and adipose tissue G6PD activity in aging rats.