Effects of indigestible dietary bulk and short chain fatty acids on the tissue weight and epithelial cell proliferation rate of the digestive tract in rats.

Influences of indigestible dietary bulk (kaolin), short chain fatty acids (SCFA), and their interaction on the weight and epithelial cell proliferation rate of digestive organs were studied. Rats with an ileal fistua were fed an elemental diet with or without kaolin (10% w/w). They were given a 3 ml SCFA mixture (acetate, propionate, and butyrate; 100, 20, and 60 mM, respectively; pH 6.1) or a 3 ml NaCl solution (180 mM; pH 6.1) via the fistua twice a day for 14 days. Kaolin, but not SCFA, increased full and empty body weight by 14% and 13%, respectively. Kaolin increased the tissue weight, but not relative tissue weight (tissue weight/empty body weight), of the forestomach, distal colon, liver and heart by 6-14%. SCFA, independent of the presence of kaolin, increased the weight and the relative weight of the cecum, both by 15%. SCFA, but not kaolin, increased the cryptal cell production rate in colonic segments by 50-140%. These results indicate that SCFA accelerates epithelial cell proliferation, thereby increasing cecal tissue weight, kaolin stimulates body weight gain which is accompanied by a proportional increase in the tissue weight of some digestive organs, and the actions of these factors are independent of each other.