Abstract
A growing number of healthy dietary ingredients in fruits and vegetables have been shown to exhibit diverse biological activities. Phloretin, a dihydrochalcone flavonoid that is abundant in apples and pears, has anti-inflammatory effects on ulcerative colitis (UC) mice. The gut microbiota and metabolism are closely related to each other due to the existence of the food-gut axis in the human colon. To investigate the interplay of faecal metabolites and the microbiota in UC mice after phloretin treatment, phloretin (60 mg/kg) was administered by gavage to ameliorate dextran sulfate sodium (DSS)-induced UC in mice. Gut microbes and faecal metabolite profiles were detected by high-throughput sequencing and liquid chromatography mass spectrometry (LC-MS) analysis, respectively. The correlations between gut microbes and their metabolites were evaluated by Spearman correlation coefficients. The results indicated that phloretin reshaped the disturbed faecal metabolite profile in UC mice and improved the metabolic pathways by balancing the composition of faecal metabolites such as norepinephrine, mesalazine, tyrosine, 5-acetyl-2,4-dimethyloxazole, and 6-acetyl-2,3-dihydro-2-(hydroxymethyl)-4(1H)-pyridinone. Correlation analysis identified the relations between the gut microbes and their metabolites. Proteus was negatively related to many faecal metabolites, such as norepinephrine, L-tyrosine, laccarin, dopamine glucuronide, and 5-acetyl-2,4-dimethyloxazole. The abundance of unidentified Bacteriodales_S24-7_group was positively related to ecgonine, 15-KETE and 6-acetyl-2,3-dihydro-2-(hydroxymethyl)-4(1H)-pyridinone. The abundance of Christensenellaceae_R-7_group was negatively related to the levels of 15-KETE and netilmicin. Stenotrophomonas and 15-KETE were negatively related, while Intestinimonas and alanyl-serine were positively related. In conclusion, phloretin treatment had positive impacts on faecal metabolites in UC mice, and the changes in faecal metabolites were closely related to the gut microbiota.