Plasma enteroglucagon, gastrin and peptide YY in conventional and germ-free rats refed with a fibre-free or fibre-supplemented diet.

Germ-free rats and conventional rats were starved and then refed with either an elemental diet (Flexical), or Flexical plus 30% kaolin, or Flexical plus 30% of a fibre mixture. Plasma levels of enteroglucagon, gastrin and peptide YY (PYY) were all significantly affected by diet. Enteroglucagon and especially PYY were significantly increased by the addition of fermentable fibre to the diet, but only in the conventional, not in the germ-free rats. Gastrin was not affected by the addition of fermentable fibre, but was increased by kaolin. Enteroglucagon and PYY were, however, both very much elevated in the germ-free animals, in which there is no proliferative response to fibre. Enteroglucagon and PYY levels were similar to those usually associated with extreme hyperproliferative states, indicating that it is unlikely that these hormones are involved in the proliferative response of the gastrointestinal tract to dietary fibre, and casting doubt on their role in other responses.