Adrenal modulation of the enhanced fat intake subsequent to fasting

Abstract

Elevations in corticosterone have been linked with the enhanced fat appetite of genetically obese Zucker rats. The present study set out to describe the effects of elevations in corticosterone in adult male Sprague-Dawley rats. Previous studies have shown that food deprivation leads to a time-dependent increase in basal corticosterone concentrations. It was predicted that rats would select a high fat diet during initial refeeding subsequent to a 24-hour fast and more severe food deprivation (48 hours) would promote greater fat consumption. Dependence upon adrenal hormones for this enhanced fat intake was examined with adrenalectomized animals. It was hypothesized that adrenalectomy would prevent the increase in fat intake seen in intact animals. Two experiments were performed. In the first, rats were given access to three separate macronutrient sources and allowed to self-select a diet for 7 days. They were then divided into groups and deprived of food for 0, 24, or 48 hours. At the end of the restriction period each rat was tail bled and macronutrient access was restored. Intakes were measured and blood samples taken at 1, 3, 6, 12, and 24 hours following restored access. During the first hour of refeeding, food-deprived animals ate significantly more fat than nondeprived animals. The enhanced fat intake was positively correlated with the elevations in corticosterone observed at the start of the refeeding period (r=.72). In the second experiment, rats were allowed to self-select a diet for 9 days. On Day 10 the rats received either bilateral adrenalectomies or sham operations. They were allowed to recover for 5 days. On Day 15 they were assigned to deprivation groups and deprived of food for 0, 24, or 48 hours. After their respective restriction periods, the rats were tail bled and food access was restored. During the first hour of refeeding, sham animals deprived of food ate significantly more fat than all other groups. Enhanced fat intake was not observed in the adrenalectomized animals, suggesting that adrenal hormones mediate dietary fat intake.