High-Starch Diet Consumption Impaired Intestinal Barriers of Juvenile Largemouth Bass (Micropterus Salmoides)

Abstract The intestinal barrier is primarily composed of physical, physiological and microbial barriers, and intestine microbe-immune interactions influenced by diet in fish still remain increasingly unexplored. The intestinal barriers of Largemouth bass (Micropterus salmoides) (4.1±0.2g) were explored after they were fed three different starch diets for eight weeks (low starch,7%; middle starch, 12%; high starch, 17%). The results showed that high starch diet led slight infiltration of inflammatory cells and moderate loss of mucous membrane layer in midgut. Meanwhile, high starch diet decreased the antioxidant enzymes (T-SOD) activities and genes (SOD1, SOD2, SOD3a, CAT, GPX) expression significantly (P < 0.05). The MDA content was significantly increased with increasing starch level (P < 0.05). High starch diet up-regulated the expression of pro-inflammatory genes (IL-8, IL-1β and TNFα) and apoptosis genes (bax, caspase3, caspase8 and caspase9), whereas down-regulated the expression of anti-apoptosis genes bcl-2 and tight junction proteins genes (occludin and claudin7). In addition, the high starch diet increased the relative abundance of Actinobacteria and Firmicutes, resulted in microbial dysbiosis. In conclusion, high dietary starch impaired intestinal barriers, and increased the risk of disease outbreaks.