Plasma cholecystokinin and pancreatic growth during adaptation to dietary protein

Abstract

The relationship among plasma cholecystokinin (CCK), pancreatic growth, and food intake was studied in rats over a 2-wk period of adaptation from a very low-protein to a very high-protein diet. Rats adapted to a control diet (5% casein) were killed at 0900 (without fasting) at 0 h, 12 h, 24 h, 48 h, 7 days, or 14 days after transfer to a high-protein diet (75% casein). CCK was measured by bioassay using isolated pancreatic acini. Plasma CCK in high protein-fed rats was increased approximately threefold in the first 24 h, but returned to control (approximately 2.5 pM) values by day 7. Pancreatic weight, DNA, protein, and chymotrypsin(ogen) significantly increased to maximal values by day 7 in high protein-fed rats. Food intake in high protein-fed rats was inhibited by 47% after 24 h but returned to control values by day 7. The results indicate that high-protein diets initially increase CCK release and increase pancreatic protease secretory capacity and that, when pancreatic protease secretion is sufficient to match protein digestive requirements, the stimulus for CCK secretion is reduced and plasma CCK returns to normal. The pronounced but transient inhibition of food intake in high protein-fed rats is consistent with a role for CCK in regulation of food intake.

Regulation of Pancreatic Secretion

“…165 It was also shown that dietary proteins that effectively stimulated CCK secretion were ineffective with the co-administration of exogenous trypsin 58 . 260 During the first few days of feeding a high-casein diet, plasma CCK levels were very high. 257 Substantial evidence indicated that CCK mediated the effects of trypsin inhibitor feeding and bile-pancreatic juice diversion on pancreatic growth.…”

Molecular Mechanisms of Pancreatic Dysfunction Induced by Protein Malnutrition

“…Consumption of large amounts of protein induces growth of the adult rodent pancreas 5, 6. Dietary protein stimulates the release of gastrointestinal hormones and the growth promoting effects of dietary protein on the exocrine pancreas have been attributed to these hormones, particularly cholecystokinin (CCK) 7.…”

Specific adaptation of gastric emptying to diets with differing protein content in the rat: is endogenous cholecystokinin implicated?

“…When compared with healthy controls, in patients with anorexia nervosa, an earlier and greater rise in plasma CCK levels after a liquid meal was observed, a pattern which was normalised with nutrition therapy 18. Animal experiments have shown that—during adaptation to increased dietary proteins—there is a notable, although transient, increase in plasma CCK levels 19. On the contrary, after food deprivation, plasma CCK levels decrease rapidly and this decrease is followed by a reduction in duodenal CCK mRNA and mucosal CCK peptide levels.…”