Effects of duodenal fat, protein or mixed-nutrient infusions on epigastric sensations during sustained gastric distension in healthy humans.

Duodenal fat modulates sensory and motor responses to gastric distension and raises plasma cholecystokinin compared with glucose. The effects of protein (also releasing cholecystokinin), or mixed nutrients (with a balanced macronutrient composition), on gastrointestinal sensations in relation to gastric relaxation and plasma cholecystokinin concentrations are not known. The aim of this study was therefore to compare the effects of duodenal infusion of fat, protein or mixed nutrients during sustained gastric distension (mimicking the intragastric presence of food) on these parameters. In 10 healthy subjects, gastric distension to fullness was maintained for 90 min, while gastric volume, sensations and plasma cholecystokinin were monitored during duodenal infusion of isotonic saline or nutrients (2 kcal min-1). During saline infusion, all parameters remained unchanged for 90 min. Initially, only lipid increased plasma cholecystokinin, gastric volume and scores for sensations. Cholecystokinin and gastric volume responses to protein and mixed nutrients were delayed and not associated with significant changes in sensations. In conclusion, the intensity of gastrointestinal sensations is related to, but not entirely explained by, the magnitude in intragastric volume and plasma cholecystokinin changes. Our results offer new insights into the role of dietary nutrient composition in gastrointestinal sensations, and may have implications for the dietary management of digestive symptoms.