Traditional Processed Meat Products Re-designed Towards Inulin-rich Functional Foods Reduce Polyps in Two Colorectal Cancer Animal Models

Inulin-rich foods exert a prebiotic effect, as this polysaccharide is able to enhance beneficial colon microbiota populations, giving rise to the in situ production of short-chain fatty acids (SCFAs) such as propionic and butyric acids. These SCFAs are potent preventive agents against colorectal cancer due to their histone deacetylases inhibitory properties, which induce apoptosis in tumor colonocytes. As colorectal cancer is the fourth most common neoplasia in Europe with 28.2 new cases per 100,000 inhabitants, a cost-effective preventive strategy has been tested in this work by redesigning common porcine meat products (chorizo sausages and cooked ham) consumed by a substantial proportion of the population towards potential colorectal cancer preventive functional foods. In order to test the preventive effect of these inulin-rich meat products against colorectal cancer, an animal model (Rattus norvegicus F344) was used, involving two doses of azoxymethane (10 mg/kg) and two treatments with dextran sodium sulfate (DSS) during a 20-week assay period. Control feed, control sausages, functional sausages (15.7% inulin), control cooked ham and functional cooked ham (10% inulin) were used to feed the corresponding animal cohorts. Then, the animals were sacrificed and their digestive tract tissues were analyzed. The results showed a statistically significant 49% reduction in the number of colon polyps in the functional meat products cohorts with respect to the control meat products animals, as well as an increase in the cecum weight (an indicator of a diet rich in prebiotic fiber), a 51.8% increase in colon propionate production, a 39.1% increase in colon butyrate concentrations, and a reduction in the number of hyperplastic Peyer's patches. Metagenomics studies also demonstrated colon microbiota differences, revealing a significant increase in Bacteroidetes populations in the functional meat products (mainly due to an increase in Bacteroidaceae and Prevotellaceae families, which include prominent propionate producers), together with a reduction in Firmicutes (especially due to lower Lachnospiraceae populations). However, functional meat products showed a remarkable increase in the anti-inflammatory and fiber-fermentative Blautia genus, which belongs to this Lachnospiraceae family. The functional meat products cohorts also presented a reduction in important pro-inflammatory bacterial populations, such as those of the genus Desulfovibrio and Bilophila. These results were corroborated in a genetic animal model of CRC (F344/NSlc-Apc1588/kyo) that produced similar results. Therefore, processed meat products can be redesigned towards functional prebiotic foods of interest as a cost-effective dietary strategy for preventing colorectal cancer in human populations.

Mucosal microbiota of intestinal polyps reveals putative biomarkers of colorectal cancer

The human intestine retains a complex microbial ecosystem, which performs crucial functions that impact on host health. Several studies have indicated that intestinal dysbiosis may impact on the establishment of life-threatening intestinal diseases such as colorectal cancer. An adenomatous polyp is the result of abnormal tissue growth, which is benign but is considered to be associated with a high risk of developing colorectal cancer, based on its grade of dysplasia. Development of diagnostic tools that are based on surveying the gut microbiota and are aimed at early detection of colorectal cancer represent highly desirable target. For this purpose, we performed a pilot study in which we applied a metataxonomic analysis based on 16S rRNA gene sequencing approach to unveil the composition of microbial communities of intestinal polyps. Moreover, we performed a meta-analysis involving the reconstructed microbiota composition of adenomatous polyps and publicly available metagenomics datasets of colorectal cancer. These analyses allowed the identification of microbial taxa such as Faecalibacterium, Bacteroides and Romboutsia, which appear to be depleted in cancerogenic mucosa as well as in adenomatous polyps, thus representing novel microbial biomarkers associated with early tumor formation. Furthermore, an absolute quantification of Fusubacterium nucleatum in polyps further compounded the important role of this microorganism as a valuable putative microbial biomarker for early diagnosis of colorectal cancer.

Intestinal microbiota: a potential diet-responsive prevention target in ApcMin mice

We previously reported that two dietary regimens, calorie restriction (CR) and a high olive oil-containing diet supplemented with a freeze-dried fruit and vegetable extract (OFV), reduced the development of intestinal adenomas in Apc(Min) mice by 57% and 33%, respectively, compared to control mice fed a defined diet ad libitum. The OFV diet was designed to have a strong effect on the composition of the intestinal microbiota through its high content of fiber, which represents a major source of fermentable substrate for the gut bacteria. We hypothesized that some of the observed effects of diet on intestinal carcinogenesis might be mediated by diet-related changes in the bacterial species that thrive in the gut. Therefore, we determined by fluorescent in situ hybridization (FISH) and denaturing gradient gel electrophoresis (DGGE) how the dietary interventions affected the composition of the intestinal microbiota, and we characterized specific microbiota changes that were associated with diet and reduced intestinal carcinogenesis. The OFV diet changed the overall composition of the intestinal microbiota, smaller changes were observed for the CR diet. Furthermore, we detected a 16S rDNA fragment associated with mice that did not develop polyps. Sequence analysis suggested that hitherto unidentified bacteria belonging to the family Lachnospiraceae (order Clostridiales) were its source. Thus, these bacteria may be an indicator of intestinal conditions associated with reduced intestinal carcinogenesis in Apc(Min) mice.

The effect of a probiotic drink with Lactobacillus plantarum 299v on the bacterial composition in faeces and mucosal biopsies of rectum and ascending colon

BACKGROUND

Studies on probiotics mainly base their results on faecal samples, which may not represent the situation in the mucosa of distal and proximal colon.

AIM

In a placebo-controlled study, to assess the effect of Lactobacillus plantarum 299v on the bacterial composition of faecal vs. mucosal samples.

METHODS

Twenty-nine patients undergoing colonoscopic examination for polyps consumed a twice-daily drink with or without L. plantarum 299v (10(11) CFU/day) for 2 weeks. Faecal samples were collected before and after consumption. During colonoscopy, biopsies were collected from the ascending colon and rectum. The faecal and mucosal bacterial concentrations and prevalence were determined.

RESULTS

L. plantarum 299v significantly increased the concentration of faecal lactic acid bacteria, lactobacilli and clostridia, and was identified in two rectal biopsies but not in the ascending colon biopsies of probiotic-treated subjects. Concentrations and prevalence in ascending colon and rectum biopsies were comparable, but were significantly lower compared with faecal samples.

CONCLUSIONS

After probiotic consumption, a significant increase in the faecal concentration of lactobacilli was found but concentrations were low in biopsies. The bacterial composition in biopsies of the ascending colon and rectum did not differ based on culture techniques. To further elucidate the modes of action of probiotics, it might be necessary to study differences in colonization with molecular techniques.

Inhibitory effect of intestinal bacteria on spontaneous multiple polyps in the small intestine of gnotobiotic BALB/c mice

The incidence of multiple polyps and number of polyps per mouse were significantly lower in conventionalized (CVz), and chloroform-resistant bacteria (CRB)- or fusiform bacteria (FB)-associated mice than in germfree (GF) BALB/c mice. The concentration of fecal fatty acids was also higher in mice associated with either CRB or FB than in GF mice. The incidence of multiple polyps and number of polyps per mouse were significantly correlated with the concentration of fatty acids in the feces of CVz and CRB-GB mice. This study demonstrated that inhibition of multiple polyps in the small intestine of BALB/c mice was affected by the production of intestinal fatty acids.

Inhibition of polyposis in the small intestine of BALB/c mice by intestinal bacteria

The incidence of polyposis and the number of polyps per mouse were significantly lower in conventionalized (CVz) mice than in germ-free (GF) mice. There was no significant difference in the average number of polyps between GF and gnotobiotic (GB) mice monoassociated with the various strains of intestinal bacteria. However, the incidence of polyposis and the number of polyps per mouse were significantly lower for mice associated with either chloroform-resistant bacteria (CRB) or fusiform bacteria (FB) than for GF mice. This study demonstrated that polyposis was suppressed by FB and CRB in the small intestine of BALB/c mice.

Resolution of a metaplastic duodenal polyp after cure of Helicobacter pylori infection

Although there have been several reports of hyperplastic gastric polyps associated with persistent Helicobacter pylori gastritis, the association of H. pylori infection with metaplastic polyps in the duodenum has not hitherto been described. After a 52-year-old man had a single episode of hematemesis, endoscopy showed a smooth polyp 1 cm in greatest dimension formed by a proliferation of gastric epithelial cells of fundic and antral type found in the duodenal bulb. The outer surface was entirely covered with a single layer of hyperplastic columnar epithelium with many H. pylori organisms. After administration of metronidazole 500 mg, omeprazole 20 mg for 4 weeks, and clarithromycin 250 mg twice a day for 2 weeks, endoscopy showed a decrease in size of the duodenal polyp. At 12 weeks there was complete regression of the polyp. This report documents a new and unusual finding: resolution of a gastric metaplastic polyp in the duodenum associated with cure of H. pylori.

Intestinal floras of populations that have a high risk of colon cancer

The fecal floras of polyp patients, Japanese-Hawaiians, North American Caucasians, rural native Japanese, and rural native Africans were compared. The polyp patients and Japanese-Hawaiians were considered to be groups at high risk of colon cancer, and the rural native Japanese and rural native Africans were considered to be groups at low risk. The North American Caucasians were found to have a flora composition intermediate between these two groups. Fifteen bacterial taxa from the human fecal flora were significantly associated with high risk of colon cancer, and five were significantly associated with low risk of colon cancer. Total concentrations of Bacteroides species and, surprisingly, Bifidobacterium species were generally positively associated with increased risk of colon cancer. Some Lactobacillus species and Eubacterium aerofaciens, which also produces major amounts of lactic acid, showed closest associations with low risk of colon cancer.

The association of Streptococcus bovis fecal carriage and colon neoplasia: possible relationship with polyps and their premalignant potential

We designed a study to evaluate the fecal carrier rate of Streptococcus bovis in patients with endoscopically proven colonic polyps. Benign polyps (n = 63), i.e., hyperplastic, inflammatory, and juvenile, had a similar fecal carrier rate as the normal control colons. Colons with polyps that are at increased risk for malignant degeneration (n = 62), i.e., tubulovillous and villous adenomas, and colons with carcinoma (n = 18), had a statistically significant increase (p less than 0.05) in the fecal carrier rate for S. bovis over the benign colon group. Overall, the incidence of S. bovis carriage in all colons with polyps was intermediary between normal colons and colons with carcinoma although the numbers did not achieve statistical significance.

Fecal steroid 21-dehydroxylase, a potential marker for colorectal cancer

Eubacterium lentum and phenotypically similar organisms synthesize a steroid 21-dehydroxylase which converts biliary tetrahydrodeoxycorticosterone to pregnanolone. Tetrahydrodeoxycorticosterone, in contrast to pregnanolone, is carcinogenic for hamster embryonic cells (HECT test). In patients with recently diagnosed, untreated sigmoidal or rectal cancer the fecal concentration of 21-dehydroxylating organisms is reduced by more than 99% as compared with age-matched controls. The lack of fecal 21-dehydroxylating organisms, therefore, is a potential marker for the disorder. The role of steroid 21-dehydroxylase in the pathogenesis of colorectal cancer is unknown.

Fecal profiles of anaerobic microflora of large bowel cancer patients and patients with nonhereditary large bowel polyps

It has been postulated that the intestinal anaerobes play a role in the etiology of large bowel cancer. This study was designed to characterize and compare the fecal anaerobes of patients with large bowel cancer, patients with nonhereditary large bowel polyps, and healthy control subjects. Although some distributional variations of the anaerobic genera were observed among the study groups, significant differences in fecal anaerobic microflora and total aerobic counts were not noted. This suggests that taxonomic grouping of fecal bacteria is an inadequate measure of relative risk of developing large bowel cancer. However, the fecal microbial 7alpha-dehydroxylase and cholesterol dehydrogenase activities of large bowel cancer patients and patients with nonhereditary large bowel polyps were significantly higher than those of healthy control subjects. On the other hand, no significant difference in fecal microbial beta-glucuronidase activity was noted among the study groups. It may be that assessment of the total metabolic activities of the intestinal microflora will provide a better understanding of their potential role in the genesis of large bowel cancer.

Metabolic epidemiology of colon cancer: enzymic activity of fecal flora

Because of the potential significance of secondary bile acids and cholesterol metabolites formed by the intestinal microflora in the pathogenesis of colon cancer, fecal microbial 7alpha-dehydroxylase and cholesterol dehydrogenase activities were assayed in colorectal cancer patients, patients with adenomatous polyps, asymptomatic controls, and normal controls. The mean 7alpha-dehydroxylase activity per 100 mg of dry feces per 2 hr incubation for colorectal cancer patients was significantly greater than either asymptomatic controls or normal controls. Patients with polyps had greater activity than controls, but did not differ significantly from the cancer patients or asymptomatic controls. The mean cholesterol dehydrogenase activity for colorectal cancer patients was significantly greater than controls. Patients with polyps also had greater activity than controls. No differences in the level of fecal beta-glucuronidase activity were found among the four risk groups. These data support the concept that patients with colorectal cancer are more able to convert primary bile acids and cholesterol to microbial products in colon contents than are controls. Such differences in the activity of intestinal microflora may serve as biochemical indicators that will reflect the enzymic activity of the fecal flora as well as the key intraluminal compounds in identifying populations at different risk for developing colorectal cancer.

Fecal steroids and bacterial flora in patients with polyposis coli

Fecal neutral and acid steroids and bacterial flora have been studied in a series of patients with polyposis coli and normal controls. The patients with polyposis coli showed a higher concentration of cholesterol and primary bile acids, which increased still more after ileorectostomy. The bacterial flora of the patients with polyposis coli showed an anaerobe/aerobe ratio of 2.7/1 with a relative increase in clostridia and bifidobacteria and decrease in eubacteria and bacteroides. After ileorectostomy clostridia disappear, as do rumenococcus, peptostreptococcus, and fusobacteria, whereas eubacteria and lactobacilli decrease and bifidobacteria and bacteroides increase. Eubacteria showed a decrease from normal in the pre- and postoperative patients with polyposis coli and paralleled the reduction of cholesterol to coprostanol.

Fecal bacteriology of colonic polyp patients and control patients

Feces from 25 subjects with colonic polyps (multiple adenomatous, large single, or single with atypia) and from 25 matched control subjects were studied by detailed quantitative aerobic and anaerobic techniques, using a large battery of culture media and several atmospheric conditions. Over 55% of organisms detected on microscopic count were recovered anaerobically. In several cases, there were significantly different numbers of organisms of specific types recovered from the two different populations studied. However, these differed from organisms with "statistical significance" noted in a previous study from this laboratory involving two different diet groups (Japanese Americans on either a Japanese or a Western diet). Specific differences in bacteriology between groups with different risks of bowel cancer, noted in earlier British studies, were not noted in our present or previous study.