Site specificity of fat cell lipolysis during pregnancy in two strains of rats

Abstract

The response to energy intake and expenditure is thought to be influenced by the genetic background. In the present study the metabolic response to pregnancy and to exercise training during pregnancy was investigated in two strains of rats. Lean Zucker and Wistar rats were divided into three groups: control pregnant (CP), exercise-trained pregnant (TRP), and not trained and not pregnant control (CNP). Trained rats swam 3 h per day, 6 days per week, throughout pregnancy. Body weight and food intake increased similarly during pregnancy in both strains (p ≤ 0.05). However, only Wistar rats had a further increase of food intake and body weight during the second half of pregnancy: TRP weighed 29.1 more grams and ate 4.5 more grams of food per day than CP at the end of pregnancy (p ≤ 0.05). Inguinal and parametrial fat cell sizes were unchanged during pregnancy. In both strains training induced a decrease of inguinal fat cell size at the beginning of pregnancy (p ≤ 0.05), which was rapidly counteracted to reach CP values on day 20 of pregnancy. Parametrial fat cell size was also decreased by training (p ≤ 0.05), but no values returned to control levels during pregnancy. In both strains, pregnancy increased fat cell lipolysis in the inguinal depot only (p ≤ 0.05). Training during pregnancy inhibited fat cell lipolysis in inguinal and parametrial depots, especially in Zucker (p ≤ 0.05), TRP reaching values similar to control values on day 20 of pregnancy. These results suggest that the effects of exercise training on the morphology of adipose tissue are similar in different strains of rats. They also show that the mobilization of fatty acids during pregnancy could respond to training in a strain-specific manner.Key words: adipose tissue, lipolysis, rat strain differences, pregnancy.