Relationships between gastric emptying and intestinal absorption of nutrients and energy in mini pigs

Little is known about the relationship between gastric emptying of nutrients regulated by feedback mechanisms and the absorptive capacity of the gut. Therefore, we wanted to elucidate these interrelationships. A 150-cm jejunal segment was perfused (1-8 kcal/min) with three different nutrient solutions (either 60% of energy as carbohydrate, or 60% as protein, or 33.3% of each nutrient). In separate experiments, gastric emptying was measured after administration of three different meals with the same nutrient composition as the perfusion solutions. The jejunal absorption of carbohydrate, protein, fat, and energy demonstrated saturation kinetics. The kinetics differed among the three nutrients; carbohydrates were absorbed at higher rates than fat and protein. Interactions among the nutrients altered the kinetics providing a constant absorption of energy. After meals, the stomach emptied equal amounts of energy despite large variations in meal composition. The available intestinal absorptive capacity for protein was utilized by 96%, whereas that for carbohydrate, fat and energy were utilized only by 46-62%. Besides reserves in the absorptive capacity, the intestine provided reserves in total length available for absorption. The results indicate a close relationship between the energy-dependent absorption of nutrients and the energy-dependent feedback inhibition of gastric emptying.