Are physiological changes in meal-fed rats determined by the amount of food ingested in the last meal or due to feeding schedule?

Abstract

Rats trained to eat a single meal from 0800 to 1000 AM, (MF rats), increased food intake from the 1st (7.0 g) to the 13th (16.1 g) day and showed higher hepatic glycogen concentration and glycemia during fasting. To verify if these changes were determined by the higher food intake or due to the disciplining condition we compared rats at the 1st (MF(1st day-5 g) group) and 13th day (MF(13th day-5 g) group) of training, refed with a fixed amount of food (5 g). In addition, a third group (MF(13th day-12 g) group) composed by trained meal-fed rats, refed on day 13 with approximately 75% of food ingested by MF rats on day 13 ( 12 g) of feeding training was included. The experiments with these 3 groups were performed at zero (1000 h), 6 (1600 h), 13 (2300 h), 18 (0400 h) and 22 (0800 h) h after meal. Our results demonstrated that part of the physiological changes of MF rats is consequence of feeding training (increased food intake during the fixed meal time and spontaneous elevation of glycemia 13 h after meal) and part of the differences (hepatic glycogen concentration, gastric and intestinal emptying) correlate well with effective time of fasting. In addition, hepatic gluconeogenesis from L-lactate and glycerol was influenced by both factors.