Dig Dis Sci. 2013 Jun;58(6):1717-26.

Changes of the intestinal microbiota, short chain fatty acids, and fecal pH in patients with colorectal cancer.

Ohigashi S, Sudo K, Kobayashi D, Takahashi O, Takahashi T, Asahara T, Nomoto K, Onodera H.

Department of Gastroenterological Surgery, St. Luke’s International Hospital, 9-1 Akashi-cho Chuo-ku, Tokyo, 104-8560, Japan. ohigashiseiji@ab.auone-net.jp

 

Abstract

BACKGROUND: New molecular biology-based methods of bacterial identification are expected to help elucidate the relationship between colorectal cancer (CRC) and intestinal microbiota. Although there is increasing evidence revealing the potential role of microbiota in CRC, it remains unclear whether microbial dysbiosis is the cause or the result of CRC onset.

AIM: We investigated the changes of intestinal environments in CRC or adenoma.

METHODS: We analyzed 13 groups of microbiota, 8 types of organic acids, and pH in feces obtained from the following 3 groups: individuals with CRC, adenoma, and non-adenoma. Ninety-three patients with CRC and 49 healthy individuals (22 with adenoma and 27 without adenoma) were enrolled.

RESULTS: The counts of total bacteria (10.3 ± 0.7 vs. 10.8 ± 0.3 log10 cells/g of feces; p < 0.001), 5 groups of obligate anaerobe, and 2 groups of facultative anaerobes were significantly lower in the CRC group than in the healthy individuals. While the concentrations of short chain fatty acids (SCFAs) were significantly decreased in the CRC group, the pH was increased in the CRC group (7.4 ± 0.8 vs. 6.9 ± 0.6; p < 0.001). Comparison among the CRC, adenoma, and non-adenoma groups revealed that fecal SCFAs and pH in the adenoma group were intermediate to the CRC group and the non-adenoma group. Within the CRC group, no differences in microbiota or organic acids were observed among Dukes stages.

CONCLUSIONS: CRC patients showed significant differences in the intestinal environment, including alterations of microbiota, decreased SCFAs, and elevated pH. These changes are not a result of CRC progression but are involved in CRC onset.

PMID: 23306850

 

Supplement:

The relationship between colorectal cancer (CRC) and fecal microbiota has been examined, and the potential role of microbiota in CRC has been generated using newly developed techniques such as the reverse transcription – quantitative polymerase chain reaction. However, there is one question that has yet to be fully elucidated: are the changes in microbiota in CRC patients a result or a cause of the initiation of CRC?

The results gained from our current study are;

(1)    Patients with CRC showed significant differences in the intestinal environment, including alterations of microbiota (decrease in so-called beneficial bacteria), decreased organic acids (particularly short chain fatty acids) concentrations, and elevated fecal pH.

(2)    Concentrations of short chain fatty acids and pH in the adenoma group were intermediate to the CRC group and the non-adenoma group (Fig. 1).

(3)    Within CRC patients, no differences in either microbiota or organic acids were observed among T-stages or Dukes stages.

In summary, we have concluded that significant differences in the intestinal environment of patients with CRC are not a result of CRC progression but rather are involved in CRC onset. We believe that these results could be applicable to the prevention of CRC or to the identification of a high risk group for CRC.

Seiji Ohigashi-1Fig. 1: Comparison of organic acids and pH among the CRC group, adenoma group, and non-adenoma group. Organic acid concentrations (μmol/g of feces) and pH are expressed as the mean ± SD. Significant differences were observed between the CRC group and the non-adenoma group, while no difference was observed between the CRC group and the adenoma group (Bonferroni method); the concentrations of total organic acids, acetic acid, valeric acid and fecal pH in the adenoma group were intermediate to the CRC group and the non-adenoma group.

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