Effect of Bifidobacterium longum and inulin on gut bacterial metabolism and carcinogen-induced aberrant crypt foci in rats

Abstract

The effect of Bifidobacterium longum (4 x 10(8) viable cells/g diet) and a derivative of inulin ('Raftiline HP'; 5% w/w in diet) on colonic aberrant crypt foci (ACF) induced by the colon carcinogen azoxymethane (AOM) has been studied. The concentration of ammonia, a putative tumour promoter produced by bacterial degradation of protein and urea, and the activities of certain bacterial enzymes thought to play a role in colon carcinogenesis, beta-glucuronidase and beta-glucosidase were also assayed. Consumption of either B. longum or inulin was associated with a decrease (26 and 41%, respectively) in AOM-induced small ACF (i.e. those comprising 1-3 aberrant crypts per focus). Combined administration of the bifidobacterium and inulin resulted in more potent inhibition of ACF than administration of the two separately, achieving 80% inhibition of small ACF. Furthermore, the combined administration significantly decreased the incidence (by 59%) of large ACF (>4 aberrant crypts per focus), which are considered to be predictive of eventual tumour incidence. Since the dietary treatments were started 1 week after the carcinogen dose, the results suggest that B. longum and inulin may be affecting the early promotion phase of the carcinogenic process. Consumption of diets containing B. longum, inulin or both were also associated with decreases in beta-glucuronidase activity and ammonia concentration in the caecal contents. Both these factors have been associated with carcinogenesis of the colon in experimental animal models. In rats given inulin-containing diets (with or without B. longum) an increase in caecal wt and beta-glucosidase activity and a decrease in caecal pH were observed. The results suggest that consumption of B. longum or inulin was associated with potentially beneficial changes in caecal physiology and bacterial metabolic activity in relation to tumour risk and in the incidence of putative preneoplastic lesions in the colon. The results also indicated that combined treatment with the two agents was more effective in reducing colonic lesions.

Nutrition and cancer: A review of the evidence for an anti-cancer diet

“…Some of the best results were obtained with a probiotic strain consumed with inulin, a type of fructooligosaccharide. Total aberrant crypt foci, chemically induced, were reduced 74% by the treatment of rats with inulin and B. longum , but only 29 and 21% by B. longum and inulin alone, respectively [164]. There was a synergistic effect in using both products together.…”

Functional Aspects of Pro- and Prebiotics A literature review on immune modulation and influence on cancer

“…In the same assay, inulin, a component of chicory containing a mixture of NDOs of different degree of polymerisation also suppressed the number of aberrant crypt foci. Furthermore, a combination of inulin plus B. longum in the diet resulted in even more powerful inhibitory effect on the preneoplastic lesions than either component alone (25).…”

Chemopreventive Potential of Probiotics and Prebiotics

“…Feeding B. longum resulted in a significant change for cecal pH and weight in rats [29]. Secondary bile acids and carcinogenic compounds, exert cytotoxic and proliferative effects on colonic epithelium and increase tumor formation.…”