Aberrant crypt formation accompanies an increase of opportunistic pathogens/bacteria in the inflammatory gut of C57BL/6 mice fed a high‐fat diet

Abstract

Obesity and high fat diet are risk factors for colon cancer, but the mechanism of this relationship remains to be determined. We tested the hypothesis that a high fat diet promotes the formation of aberrant crypt foci (ACF, preneoplastic lesions) in a manner associated with changes in hindgut bacterial taxa. We examined the susceptibility to azoxymethane (AOM)‐induced colonic ACF and microbiome composition in C57/BL6 mice fed a low fat (LF, 10% energy fat) diet or a high fat (HF, 45% energy fat) diet for 11 weeks. Mice receiving the HF diet exhibited increased plasma leptin, body weight, body fat composition and inflammatory cell infiltration in the ileum compared with those in the LF group. Consistent with a gut inflammatory phenotype, we observed an increase in colonic ACF, plasma interleukin 6 (IL6), tumor necrosis factor α (TNF α), monocyte chemoattractant protein 1 (MCP1), and inducible nitric oxide synthase protein in the ileum of the HF‐AOM group compared with those in the LF‐AOM group. Fecal DNA was extracted and 16S universal eubacterial primers were utilized to determine the microbiome composition using an amplicon pyrosequencing method. Although the HF and LF groups did not differ in bacterial alpha‐diversity, the HF and LF diets resulted in unique bacterial community structures in the hindgut. When treated with AOM, the abundance of certain short chain fatty acid (SCFA) producing bacteria (e.g., Barnesiella) and the amount of fecal SCFA (e.g., acetic acid) were lower in the HF group compared with those in the LF group. Furthermore, we identified a high abundance of Anaeroplasma bacteria (opportunistic pathogens), accompanied with ACF formation in the HF group. Taken together, we demonstrate that HF feeding promotes ACF formation associated with an increase of opportunistic pathogens / bacteria in the hindgut of C57BL/6 mice.Support or Funding InformationThis work was funded by the US Department of Agriculture, Agricultural Research Service, Research Project 3062‐51000‐050‐00D.