Quercetin alleviates intestinal inflammation and improves intestinal functions via modulating gut microbiota...

Quercetin, a well-known flavonoid, has been demonstrated to exert beneficial effects on intestinal functions and gut microbiota in birds. In this study, we investigated the effects of quercetin supplementation on inflammatory responses, intestinal barrier functions and gut microbial community in LPS-challenged laying hens. A total of two hundred eighty-eight 32-wk-old Jingfen No.6 laying hens were randomly assigned to 3 groups, the CON group, the LC group and the LQ group. LQ group was fed with 0.4 mg/kg quercetin and at the end of 12 wk, LC and LQ groups were challenged intraperitoneally with lipopolysaccharide (LPS). After LPS challenge, 8 birds of each group were randomly selected and sampled. LPS challenge induced an obvious intestinal mucosal injury, necrosis and shedding, while quercetin intervention maintained its structure. Quercetin significantly decreased the elevated malondialdehyde contents (P < 0.05), and increased the activity of total antioxidant capacity and glutathione peroxidase (P < 0.05) in intestinal mucosa of LPS-challenged laying hens. Quercetin rescued the LPS-induced decreases in goblet cell density and mucin2 expression levels (P < 0.05). There was a significant decline (P < 0.05) in the mRNA expression of Claudin1 and Occludin in intestinal mucosa of LPS-challenged layers, which could be alleviated (P < 0.05) by dietary quercetin. LPS challenge induced the increased expression levels (P < 0.05) of IL-1β and TLR-4 in intestinal mucosa, while these rises could be reversed (P < 0.05) following dietary quercetin supplementation. LPS challenge induced a shift in gut microenvironment, and quercetin addition could elevate the relative abundance of some short chain fatty acids (SCFA)-producing or health-promoting bacteria such as Phascolarctobacterium, Negativicutes, Selenomonadales, Megamonas, Prevotellaceae, and Bacteroides_salanitronis. In conclusion, dietary quercetin addition ameliorated the LPS challenge-induced intestinal inflammation and improved intestinal functions, possibly associated with its modulation on gut microbiota, particularly the increased population of SCFA-producing bacteria.