Absorption and Utilization of Glucose by Meal-fed and Nibbling Rats

Abstract

The absorption and utilization of glucose by meal-fed (animals having access to food for a single, daily, 2-hour period) and nibbling (fed ad libitum) rats was studied. Meal-fed rats absorbed glucose more rapidly than nibbling animals and this enhanced absorptive rate could be explained by an increase in the weight of the small intestine. The weight of the intestine relative to body weight and the glucose absorption coefficient were both increased by about 40% in the meal-fed as compared with the nibbling animal. As a consequence of the enhanced glucose absorption rate the amount of glucose entering the blood stream, per unit time, would be approximately 40% greater in the meal-fed animal. Yet, blood glucose levels increased more slowly in meal-fed than in nibbling rats following the oral administration of glucose. The rate of utilization of absorbed glucose was significantly greater in meal-fed as compared with nibbling rats. Also, the rate of glycogen storage in muscle (abdominal, gastrocnemius and diaphragm) following food ingestion was significantly greater for meal-fed than for nibbling animals. The physiological significance of these findings and the possible regulatory mechanisms involved are discussed.