Association between low colonic short-chain fatty acids and high bile acids in high colon cancer risk populations - PubMed (original) (raw)

Association between low colonic short-chain fatty acids and high bile acids in high colon cancer risk populations

Junhai Ou et al. Nutr Cancer. 2012.

Abstract

We propose that the influence of diet on colon cancer risk is mediated by the microbiota. To investigate how dietary fat influences risk, we compared the colonic contents of 12 adult high-risk African Americans (AAs) and 10 Caucasian Americans (CAs) who consumed a high-fat diet (123 ± 11 g/d and 129 ± 17 g/d, respectively) to 13 native Africans (NAs) who subsisted on a low-fat (38 ± 3.0 g/d) diet, all aged 50-60 yr. The colonic bile acids were measured by LC-MS and the short-chain fatty acids (SCFAs) by GC. The chief secondary colonic bile acids, deoxycholic acid and lithocholic acid, were correlated with fat intake and similar between AAs and CAs, but 3-4 times higher than in AAs (p < 0.05). The major SCFAs were lower in AAs (p < 0.001) and CAs (p < 0.001) compared to AAs, but conversely, the branched chain fatty acids (BFCA) were higher. Our results suggest that the higher risk of colon cancer in Americans may be partly explained by their high-fat and high-protein, low complex carbohydrate diet, which produces colonic residues that promote microbes to produce potentially carcinogenic secondary bile acids and less antineoplastic SCFAs. The role of BCFA in colonic carcinogenesis deserves further study.

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Figures

FIG. 1.

FIG. 1.

Major bile acid contents in evacuates were significantly lower in Native Africans (NAs) compared to African Americans (AAs) and Caucasian Americans (CAs). *P < 0.05 vs. NAs, Mann-Whitney testing. There was no difference between AAs and CAs. LCA data has been magnified 10 times in order to be visible on this scale. Bile acid abbreviations: LCA, lithocholic acid; CA, cholic acid; DCA, deoxycholic acid.

FIG. 2.

FIG. 2.

Correlation between dietary fat intake calculated from 3-day recall and total colonic bile acids in all 3 population groups showing a weak but significant association (P = 0.01).

FIG. 3.

FIG. 3.

Major short-chain fatty acid concentrations in stools (left) and in colonic evacuates [right, previously reported in O’Keefe et al. (9)] were significantly higher in Native Africans (NA) compared to African Americans (AA) and Caucasian Americans (CA). **P < 0.001 vs. CA and AA; *P < 0.05 vs. CA and AA, Mann-Whitney testing. There were no significant differences between AA and CA.

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