The Effect of Synbiotics on Colon Carcinogenesis in Rats

Abstract

Evidence indicates that consumption of probiotic microorganisms such as bifidobacteria reduces the risk of colon cancer in animal models. Feeding certain fructans such as oligofructose and inulin, which are thought to selectively increase the growth of intestinal bifidobacteria (i.e., a prebiotic effect), also has been shown to reduce colon cancer risk. The objective of our study was twofold, i. e., to determine whether the combination of bifidobacteria and oligofructose would have an additive effect (i.e., synbiotic) in reducing colon cancer risk in rats, and to determine whether other oligosaccharides would also be effective as part of a synbiotic combination. The development of colonic preneoplastic lesions (aberrant crypts) was used as an index of colon cancer risk. In one series of experiments, rats were given the carcinogen 1, 2-dimethylhydrazine (DMH) and administered one of the following treatments: skim milk (control), bifidobacteria (bifido), oligofructose (OF) or bifido + OF. Neither bifido nor OF alone significantly reduced aberrant crypt number. Bifido + OF reduced aberrant crypt number in five of six experiments, although the reduction was significant in only one. However, a paired comparison of the six experiments indicated a significant overall reduction in aberrant crypts by bifido + OF (P = 0.039). Soybean oligosaccharide (SBO) and wheat bran oligosaccharide (WBO) were also fed in combination with bifidobacteria. In two other experiments, SBO did not alter the number of aberrant crypts compared with the control, whereas WBO reduced aberrant crypt number in one experiment but not in another. Of OF, SBO and WBO, only SBO reduced the colonic mucosa proliferation compared with the control. These results suggest that the combination of bifidobacteria and oligofructose reduces colon cancer risk in carcinogen-treated rats, but the effect of other oligosaccharides is uncertain.

Modulation of Rat Cecal Microbiota by Administration of Raffinose and Encapsulated Bifidobacterium breve

“…Introduction of the synbiotic concept by Gibson and Roberfroid (17) promoted application of a potential nonindigenous probiotic strain and its preferred carbon source to increase the level of the administered strain in the intestine. Several previously published works on synbiotic application described modulation of the intestinal microbiota (1,7,8,32,44), reduction of colon carcinogenesis (12,16,28), and protection from pathogen infection (6). Recently, synbiotic therapy for improvement of intestinal function (19,20) or reduction of pathogenic bacteria (21,22) has also been reported.…”

Probiotics - What They Are, Their Benefits and Challenges

“…These preparations aim to improve the viability of the proven probiotic in vivo as well as stimulate the indigenous gut microflora. They provide both the beneficial microbial culture and a specific substrate that can be readily available for fermentation by this culture (Gallaher & Khil, 1999). The presence of the readily fermentable substrate could enhance the survival of the probiotic.…”

Human Colonic Microbiology and the Role of Dietary Intervention: Introduction to Prebiotics

“…Most studies have been carried out in rats and looked at the reduction in number of aberrant crypt foci (cancer precursors) in rats treated with azoxymethane (a tumour promoter). Gallaher and Khil (1999) found that FOS and bifidobacteria had no effect when administered alone but as a synbiotic five out of six subjects had decreased aberrant crypt foci. Another study has shown that whilst a mixture of short and long chain FOS can decrease the number of adenomas and malignant cancers, a mixture of Lactobacillus reuteri GG and Bifidobacterium lactis Bb12 only had an effect in reducing numbers of malignant tumours.…”