Aquaculture Reports (Jun 2024)
Spiral valve intestinal barrier functions of juvenile Siberian sturgeon (Acipenser baerii) were changed by low or high-lipid diet
Abstract
The intestine serves as the primary defense mechanism safeguarding fish body against pathogen infiltration. Unlike cyprinid and salmonid fish, sturgeon features a distinctive special spiral valve structure within their intestines. Several studies propose that dietary lipid intake may impact the intestinal barrier function of fish. The presence of this influence within the special spiral valve intestine of sturgeon currently remains unresolved. This study aimed to explore the effects of a low or high-lipid diet on morphology, tight junction, antioxidant and immune performance, and intestinal microbiota in the spiral valve intestine of Siberian sturgeon (Acipenser baerii) (14.19 ± 0.07 g). Three diets with different lipid levels of 8.87 % (low lipid, LL), 16.93 % (moderate lipid, ML), and 24.88 % (high lipid, HL) were designed for a 70-day feeding experiment. Histological analysis revealed that the LL diet induced chronic proliferative inflammation and intestinal mucosa adhesion. In addition, the LL diet reduced the height of mucosal fold and microvilli while the HL diet shortened the microvilli only. The expression of claudin1 was inhibited by the LL diet while Claudin2 was stimulated by the HL diet. Both LL and HL diets suppressed the expression of occludin. Superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (T-AOC) of spiral valve intestine were not sensitive to different lipid levels, but glutathione peroxidase (GSH-Px) was decreased in fish fed with the LL, and malonaldehyde (MDA) was increased in fish fed with the HL. The sturgeons fed with LL diet had declined immunoglobulin M (IgM), IgG, tumor necrosis factor α (TNFα), interleukin 1β (IL1β), IL10, and transforming growth factor β1 (TGFβ1), while HL diet had no significant effects on them. With the increase of lipid levels, the alpha diversity of spiral valve intestinal microbiota showed a downward trend. The dominant genera were mainly clostridium_sensu_stricto_1, Bacillus, Mycoplasma, and the HL group also included Lactococcus. Fourteen differentially abundant taxa were identified by LEfSe analysis, which could be biomarkers. In conclusion, a low-lipid (8.87 %) diet damaged the mechanical barrier and reduced antioxidant and immune performance. High-lipid (24.88 %) diet decreased the height of microvilli and negatively affected tight junction proteins and intestinal microbiota.
