The effects of quercetin and taxifolin on gut microbes, digestion enzymes, antioxidant and inflammatory-related gene expression in the Chinese sucker (Myxocyprinus asiaticus)

We aimed to investigate the effects of quercetin and taxifolin on gut health in the Chinese sucker (Myxocyprinus asiaticus). Short-term exposure (96 h) was conducted by exposing Chinese sucker to 2.5 mg/L of quercetin (Q2.5), 5 mg/L of quercetin (Q5), 10 mg/L of quercetin (Q10), 2.5 mg/L of taxifolin (T2.5), 5 mg/L of taxifolin (T5), 10 mg/L of taxifolin (T10), and their combination (quercetin and taxifolin: 5 mg/L+5 mg/L, QT). Then, we analyzed intestinal microorganisms, fat composition, digestive enzyme activities, and antioxidant and inflammatory-related gene expression. Both quercetin and taxifolin had an inhibitory effect on the intestinal flora, and the higher the quercetin concentration, the better the inhibitory effect. When compared to quercetin, taxifolin inhibited harmful bacteria more efficiently and maintained the abundance of probiotics. T5 and QT reduced the content of total cholesterol (T-CHO), and QT reduced the content of triglycerides (TG) in intestinal tissues. Q5 inhibited trypsin activity, while T5 increased amylase (AMS) activity in intestinal tissues. Q5, T5, and QT increased the expression of GST, GPx4, SOD1 and CAT in the intestine. The expression levels of GST and CAT in T5 were higher than in the Q5 and QT groups. Q5, T5, and QT inhibited the expression of IL1 beta, IL6, IL8, TNF-alpha, and TNF-beta, and increased the expression levels of IL10. In summary, using taxifolin alone would be more beneficial with regards to maintaining homeostasis of the intestinal flora and increasing the antioxidant and antiinflammatory capacity of the intestinal tract. The optimal application rate of taxifolin was 5 mg/L.