Faecal bile acids and colorectal cell proliferation. The ECP Colon Cancer Working Group

Serum bile acids, programmed cell death and cell proliferation in the mucosa of patients with colorectal adenomas

BACKGROUND

Deoxycholic acid induced programmed cell death and an imbalance with cell proliferation may favour colorectal tumourigenesis according to 'in vitro' studies, but information is lacking on the relationships occurring 'in vivo' in humans.

AIMS

To evaluate whether serum deoxycholic acid is associated with programmed cell death and cell proliferation in colonic mucosa.

METHODS

In 10 patients with colorectal adenomas, we measured fasting serum levels of bile acids; and, in normal colonic mucosa, programmed cell death by the TUNEL technique and cell proliferation by immunohistochemical staining with anti-Ki67. Total and compartmental indices for both activities were calculated.

RESULTS

Among serum bile acids, only total deoxycholic acid (median: 0.89 micromol/L +/- 0.54 95% CI), showed a significant positive correlation with the total and basal compartments PCD Index (r = 0.68, p < 0.05). Total proliferation index showed no correlation with either total PCD Index, or bile acids. Within the median compartment of the crypt, cell proliferation was negatively associated with all unconjugated bile acids.

CONCLUSIONS

The positive association between deoxycholic acid and programmed cell death in the basal compartment of the crypt, and the negative association of cell proliferation and unconjugated bile acids in the median compartment, do not seem to support the co-carcinogenic effect of deoxycholic acid.

Bifidobacterium animalis strain DN-173 010 shortens the colonic transit time in healthy women: a double-blind, randomized, controlled study

BACKGROUND

A previous study has suggested that Bifidobacterium animalis DN-173 010 shortens the colonic transit time in women.

AIM

To confirm this effect and to determine whether modifications of the faecal bacterial mass and/or faecal secondary bile salts may be the explanation.

METHODS

A double-blind, cross-over study was performed. Thirty-six healthy women were studied in four consecutive 10-day periods. During periods 2 and 4, they ingested three 125 g cups per day of a fermented milk which was either a product containing B. animalis DN-173 010 or a control without bifidobacteria. Periods 1 and 3 were run-in and washout periods, respectively. The total and segmental colonic transit times were assessed using a pellet method. In 12 subjects, all stools were collected and analysed for pH, faecal weight, bacterial mass and bile acids.

RESULTS

The total and sigmoid transit times were significantly shorter during dosing with B. animalis compared to the control period. The other transit times, faecal weight, pH, bacterial mass and bile acids were not significantly affected.

CONCLUSIONS

B. animalis DN-173 010 shortens the colonic transit time in healthy women. This effect is not explained by modifications of the faecal bacterial mass or secondary bile acids.

Effect of ispaghula husk on the faecal output of bile acids in healthy volunteers

Faecal bile acids are associated with both colorectal cancer and serum cholesterol levels. We investigate whether dosing with ispaghula husk affects the faecal bile acid weights and concentrations in healthy adults. Sixteen healthy volunteers consumed 7.0 g/day ispaghula husk, containing 5.88 g/day Englyst-determinable dietary fibre, for the middle 8 weeks of a 12-week period. Stool samples were collected, analysed for faecal bile acids and their form and dry weight determined. Correlations between the faecal bile acids, the stool parameters and the dietary intake were tested. Ispaghula husk treatment significantly lowers faecal lithocholic and isolithocholic acids and the weighted ratio of lithocholic acids to deoxycholic acid. These effects revert towards their initial states at the end of the treatment period. These changes in the faecal bile acid profiles indicate a reduction in the hydrophobicity of the bile acids in the enterohepatic circulation.

Bile acids, fibre and colon cancer: the story unfolds

Are the changes in faecal bile acid concentrations the cause of colorectal cancer or one of its effects? This is an area of controversy mainly due to the lack of a clear explanation as to how the bile acid concentrations are controlled under different circumstances. This review presents an outline of the evidence that bile acids are both a causal factor in colorectal cancer and that their concentrations are affected by it in a synergistic manner. It also offers an explanation of how some dietary fibre protects against colorectal cancer.

Cell proliferation biomarkers in the gastrointestinal tract

Measurements of epithelial cell proliferation in the mucosa of the gastrointestinal tract pointed out the existence of cell kinetic abnormalities which can be involved in the first steps of carcinogenesis. In particular, an increase in the cell proliferation rate and an abnormal distribution of proliferating cells were found both in animals exposed to carcinogens and in human subjects at high risk of gastrointestinal cancer. In some diseases which predispose to cancer (i.e., chronic atropic gastritis, hereditary gastrointestinal cancer, sporadic colorectal neoplasia, chronic ulcerative colitis) we observed an expansion of the proliferative compartment even when the mucosa was not affected by morphological abnormalities. This proliferative feature seems to be associated with the presence of defects in cell differentiation. The abnormality is well detected by the histological examination of the proliferative pattern using microautoradiography after incorporation of tritiated thymidine, or using immunohistochemistry after bromodeoxyuridine uptake. The literature, and our own results, indicate that the search for abnormalities of epithelial cell proliferation can be useful in studying the earliest mechanisms leading to gastrointestinal cancer, in detecting subjects at high cancer risk, and for pilot chemoprevention studies using these abnormalities as intermediate biomarkers of gastrointestinal cancer risk.