DIETARY GUAR GUM AND PECTIN STIMULATE INTESTINAL MICROBIAL POLYAMINE SYNTHESIS IN RATS

The effects of two highly fermentable dietary fibers (guar gum and pec tin) on the type and concentrations of cecal polyamines as affected by the intestinal microflora were studied in groups of germ-free (n = 10 /group) and conventional rats (n = 6/group). Both germ-free and conven tional rats were randomly assigned to one of three treatments as follo ws: 1) fiber-free control diet, 2) control diet + 10% guar gum and 3) control diet + 10% pectin. In germ-free rats, guar gum and pectin had no effect on cecal polyamine concentrations. Putrescine was confirmed to be the major endogenous polyamine within the gut lumen. in cecal co ntents of conventional rats, both guar gum and pectin led to the appea rance of cadaverine and to elevated putrescine concentrations in compa rison with the fiber-free control diet (1.35 +/- 0.15 and 2.27 +/- 0.3 2, respectively, vs. 0.20 +/- 0.03 mu mol/g dry weight, P < 0.05). The cecal cadaverine concentration was higher in pectin- than in guar-fed rats (8.20 +/- 0.89 vs. 1.92 +/- 0.27 mu mol/g dry weight, P < 0.05). Counts of total bacteria, bacteroides, fusobacteria and enterobacteri a were higher (P < 0.05) in rats fed guar gum and pectin. Bifidobacter ia were found exclusively in guar-fed rats. In vitro studies on select ed species representing the numerically dominant population groups of the human gut flora (bacteroides, fusobacteria, anaerobic cocci and bi fidobacteria) were examined for their ability to synthesize intracellu lar polyamines. These experiments demonstrated the ability of bacteroi des, fusobacteria and anaerobic cocci to synthesize high amounts of pu trescine and spermidine. Calculations based on these results suggest t hat the intestinal microflora are a major source of polyamines in the contents of the large intestine.