Dietary fiber and intestinal adaptation: effects on intestinal and pancreatic digestive enzyme activities

Male Wistar rats were fed for four weeks on defined diets containing no fiber additions, 10% levels of insoluble fiber derivatives (cellulose or alfalfa), or 5% levels of viscous fiber derivatives (pectin, guar gum, or metamucil). After an overnight fast, the pancreas was assayed for protein, amylase, lipase, trypsin, and chymotrypsin. Homogenates of small intestinal mucosa were analyzed for protein, alkaline phosphatase, invertase and thymidine kinase. There were, with few exceptions, no dietary effects on the exocrine pancreatic enzymes. The specific activities of the villus marker enzymes (invertase and alkaline phosphatase) tended to be higher in the proximal (but not middle or distal) intestines of the fiber-fed groups, while total activities were the same in all groups. In contrast, the activity of the crypt marker, thymidine kinase, was highest in the distal intestinal segments, and even higher in animals given the alfalfa, guar gum or metamucil-supplemented diets.