Trypsin and splanchnic protein turnover during feeding and fasting in human subjects

• Published in: American journal of physiology: Gastrointestinal and liver physiology 2006-02, Vol.290 (2), p.G213-G221
• Main Authors: O'keefe, Stephen J D, Lee, Ronzo B, Li, Jing, Zhou, Wen, Stoll, Barbara, Dang, Qianyu
• Format: Article
• Language: English
• Subjects: Adult; Algorithms; Amino Acids - metabolism; Body Mass Index; Diet; Duodenum - metabolism; Enteral Nutrition; Fasting - metabolism; Female; Humans; Intestinal Mucosa - metabolism; Jejunum - metabolism; Leucine - metabolism; Male; Pancreas - enzymology; Pancreas - metabolism; Proteins - metabolism; Trypsin - metabolism
• ISSN: 0193-1857; 1522-1547
• DOI: 10.1152/ajpgi.00170.2005

Knowledge of the stimulatory effects of enteral and parenteral (intravenous) feeding on the synthesis and turnover of trypsin would help in the management of acute pancreatitis, because the disease is caused by the premature activation of trypsin. To investigate this, we labeled intravenous infusions with [1-(13)C]leucine and enterals with [(2)H]leucine and measured isotope enrichment of plasma, secreted trypsin, and duodenal mucosal proteins over 6 h by duodenal perfusion/aspiration and endoscopic biopsy. Thirty healthy volunteers were studied during fasting (n = 7), intravenous feeding (n = 6), or postpyloric enteral feeding [duodenal polymeric (n = 6), elemental duodenal (n = 6), and jejunal elemental (n = 5)]. All diets provided 1.5 g x kg(-1) x day(-1) protein and 40 kcal x kg(-1) x day(-1) energy. Results demonstrated that compared with fasting, enteral feeding increased the rate of appearance (71 +/- 4 vs. 91 +/- 5 min, P = 0.01) and secretion (546 +/- 80 vs. 219 +/- 37 U/h, P = 0.01) of newly labeled trypsin and expanded zymogen stores (1,660 +/- 237 vs. 749 +/- 133 units, P = 0.03). These differences persisted whether the feedings were polymeric or elemental, duodenal, or jejunal. In contrast, intravenous feeding had no effect on basal rates. Differential labeling of the plasma amino acid pool by enteral and intravenous isotope infusions suggested that 35% of absorbed amino acids were retained within the splanchnic bed during enteral feeding and that mucosal protein turnover increased from a fasting rate of 34 +/- 6 to 108 +/- 8%/day (P < 0.05) compared with no change after intravenous feeding. In conclusion, all common forms of enteral feeding stimulate the synthesis and secretion of pancreatic trypsin, and only parenteral nutrition avoids it.