Millet Quinic Acid Relieves Colitis by Regulating Gut Microbiota and Inhibiting MyD88/NF-κB Signaling Pathway

Polyphenols are compounds derived from plant-based food possessing numerous biological activities, including inhibiting oxidative stress, suppressing inflammation, and regulating gut microbiota. In this study, we investigated the effects of quinic acid, a phenolic acid from millet, on the regulation of gut microbiota and intestinal inflammation and further discussed the possible mechanism. The results showed that quinic acid could improve the microbiota composition of the feces of patients with inflammatory bowel disease (IBD) by in vitro anaerobic fermentation by increasing the abundance of beneficial genera including Bifidobacterium, Weissella, etc., and decreasing that of harmful genera like Escherichia-Shigella. Quinic acid treatment could alleviate the symptoms of dextran sodium sulfate (DSS)-induced colitis in mice, maintain the intestinal barrier, down-regulate the expression of inflammatory factors such as IL-1β and TNF-α, and inhibit the activation of the MyD88/NF-κB signaling pathway. In addition, quinic acid also improved the diversity of gut microbiota in mice with colitis. Furthermore, pseudo-germ-free colitis mice proved that the effect of quinic acid on intestinal inflammation was diminished after removing most gut microbiota by antibiotic treatment, suggesting that gut microbiota play important roles during the regulation of colitis by quinic acid. In a word, our study verified the regulatory effects of quinic acid on intestinal inflammation, depending on gut microbiota regulation and NF-κB signaling suppression.