FERMENTABLE CARBOHYDRATES ELEVATE PLASMA ENTEROGLUCAGON BUT HIGH-VISCOSITY IS ALSO NECESSARY TO STIMULATE SMALL-BOWEL MUCOSAL CELL-PROLIFERATION IN RATS

Enteroglucagon is a collective term for a small family of peptides der ived from proglucagon by post-translational processing in the L-cells of the distal small intestine and colon. There is evidence that it inh ibits gastric secretion, and high levels of enteroglucagon occur in pl asma during intestinal adaptation, which suggests that it may also fun ction as a trophic Factor for the intestine. Certain types of soluble nonstarch polysaccharide (dietary fiber) stimulate the release of ente roglucagon in rats but the mechanism is unknown. In this study we expl ored the importance of the viscosity and fermentability of nonabsorbed carbohydrates as determinants of plasma enteroglucagon and mucosal ce ll proliferation in the distal ileum of rats. Replacement of cellulose (10 g/kg) with guar gum in a semisynthetic diet led to a prompt and s ustained rise in plasma enteroglucagon concentrations. Our initial hyp othesis that this was a consequence of delayed nutrient absorption was disproven by the fact that hydroxypropylmethylcellulose (HPMC), a vis cous but nonfermentable polysaccharide, had no effect on plasma entero glucagon under the same conditions. In contrast, the nondigestible dis accharide lactitol led to a prolonged rise in plasma enteroglucagon, s imilar to that observed with guar gum. Lactitol is nonviscous, but hig hly fermentable, and we conclude that fermentable carbohydrate is an i mportant stimulus for the release of enteroglucagon under our experime ntal conditions. There was no evidence that enteroglucagon released by this mechanism exerted trophic effects on the distal small intestinal mucosa.