Influence of various nutrients and their mode of application on plasma cholecystokinin (CCK) bioactivity

Summary

CCK is known to be a major endocrine stimulant of the exocrine pancreas. However, the influence of various compositions of nutrients and their mode of administration on plasma CCK is still not clear. We therefore studied plasma CCK after either oral or intraduodenal administration of various solid and liquid diets. Plasma CCK was measured by bioassay. Nine healthy male volunteers received three different isocaloric diets via intraduodenal perfusion (1 kcal/ml; 300 ml/90 min). Diet A consisted of low-molecular oligopeptides (energy: protein 18%, fat 22%, carbohydrates 60%); diet B was a high molecular diet enriched with fat and fiber (protein 15%, fat 30%, carbohydrates 55%, fiber 1 g/100 ml); and diet C was a high molecular diet, poor in fat and fiber-free (protein 14%, fat 7%, carbohydrates 79%). All diets caused a rapid increase in plasma CCK, followed by a slow decrease. The highest CCK plasma values were achieved with diet B (8.4±1.6 pM); diets A and C led to similar, rather low plasma CCK values (A: 5.0±0.7 pM). Another five volunteers received the above-described liquid diets orally. Integrated CCK plasma values were similar for all oral liquid diets studied and not different from those seen after intraduodenal administration of the high-molecular high-fat diet B. Oral administration of a solid diet (ten volunteers) comparable to diet B in calories and nutrient composition caused a rather small and delayed increase in plasma CCK. Surprisingly, oral administration of a diet very rich in calories, especially fat, which caused complete satiety (spaghetti with ground beef, lettuce, banana; 1713 kcal, fat 34%, protein 16%, carbohydrates 50%; seven volunteers) resulted in maximum CCK values of only 7.3±1.2 pM. We conclude that, despite the significant differences in plasma CCK in relation to nutrient composition and mode of administration, all of the diets tested caused significant rises in plasma CCK.