The effect of menthol supplement diet on colitis-induced colon tumorigenesis and intestinal microbiota

Natural phytochemicals are extensively considered to potentially ameliorate or reverse the pathological progression of colitis-associated colon cancer (CAC). The present study aimed to evaluate the therapeutic effect of menthol on CAC and the promoting effect on the gut microbiome and metabolites. In this study, azoxymethane (AOM) combined with dextran sulfate sodium (DSS) was adopted to build CAC mouse models. H&E staining was performed to identify the pathological damage of colon tissue. By immunohistochemistry and immunofluorescence, the expression levels of β-catenin and Ki67 were measured. The mRNA expression of inflammatory cytokines and myeloperoxidase (MPO) was evaluated through RT-PCR. The infiltration of immune cells was measured by flow cytometry analysis. With 16SrDNA sequencing technology, the composition of gut microbiome were detected. To determine the concentration of short-chain fatty acids (SCFAs) in the feces, gas chromatography coupled to mass spectrometry (GC-MS) was performed. A significant inhibiting effect of menthol on AOM/DSS-induced tumorigenesis was observed, as indicated by the significantly fewer small adenomas, lower disease activity index (DAI) scores and histopathological scores, lower expression of proliferation biomarkers (β-catenin and Ki67) and pro-inflammatory cytokines (IL-6, TNF-α and MPO), and decreased immune cells infiltration. As suggested from the results of 16SrDNA sequencing, compared with AOM/DSS (AD) group, MSD exhibited higher α-diversity and shared more similar β-diversity with the control (Ctrl). Moreover, a higher abundance of butyrate-producing bacteria (Allobaculum, Roseburia and Intestinimonas) and the higher fecal butyrate concentrations were measured in the MSD compared with the AD group. MSD effectively ameliorated AOM/DSS-induced tumorigenesis and facilitated the predominant growth of butyrate-producing bacteria.