Digested soybean protein and taurine influence bile acid level, lipase activity, lipid digestibility, and growth performance of pompano (Trachinotus blochii)

Comparative Study on the Effects of Four Plant Protein Sources on the Liver and Intestinal Health of Largemouth Bass, Micropterus salmoides

The effects of plant protein sources (PPSs) on the health of the liver and intestine of the largemouth bass, Micropterus salmoides, were compared to verify the potential damaging effects of dietary fiber (DF). A diet containing 55% fish meal (FM) was used as the control. The test diets contained 25% soybean meal (SBM), rapeseed meal (RSM), cottonseed meal, or peanut meal, and the FM content was decreased to 30%. The protein and lipid contents of these five diets were balanced by casein and oil. Fish were raised for 8 weeks. The fish fed the diet containing PPS showed a trend of decreasing growth and apparent digestibility coefficients. The contents of total bile acid, lipid, and collagen in the liver were increased, and the mRNA expression levels of genes encoding inflammatory factors and enzymes involved in de novo fatty acid synthesis and bile acid synthesis were upregulated. Both the lipid and collagen contents in the liver were positively correlated with the DF content in the diet significantly. Morphology and histology showed reduced liver size, hepatic steatosis, and fibrosis in fish fed diets containing PPS. The lowest hepatosomatic index was observed in fish fed the SBM diet, and the most severe damage was observed in fish fed the RSM diet. No obvious histological abnormalities were observed in the hindgut. The bile acid profile in the liver could be used to distinguish the types of PPS very well by Fisher discriminant analysis. These results indicated that 25% of each of the four PPSs in the diet exceeded the tolerance range of largemouth bass and caused liver damage, which might be mediated by bile acid. DF in PPS might be an important agent contributing to liver damage.

Bile acids supplementation modulates lipid metabolism, intestinal function, and cecal microbiota in geese

Bile acids(BAs) are important components of bile and play a significant role in fat metabolism. However, there is currently no systematic evaluation of the use of BAs as feed additives for geese.This study aimed to investigate the effects of adding BAs to goose feed on growth performance, lipid metabolism, intestinal morphology, mucosal barrier function, and cecal microbiota. A total of 168 28-day-old geese were randomly assigned to four treatment groups and fed diets supplemented with 0, 75, 150, or 300 mg/kg of BAs for 28 days. The addition of 75 and 150 mg/kg of BAs significantly improved the feed/gain (F/G) (p  < 0.05).The addition of BAs decreased abdominal fat percentage and serum total cholesterol (TC) levels, with 150 mg/kg of BAs significantly reducing serum triglyceride levels and increased expression of Farnesoid X Receptor (FXR) mRNA in the liver(p  < 0.05), 300 mg/kg of BAs significantly increasing the expression level of liver peroxisome proliferator-activated receptor α (PPARα) (p < 0.05). In terms of intestinal morphology and mucosal barrier function, 150 mg/kg of BAs significantly increased villus height (VH) and VH/crypt depth (CD) in the jejunum (p < 0.05). The addition of 150 and 300 mg/kg of BAs significantly reduced the CD in the ileum, while increasing VH and VH/CD (p<0.05). Additionally, the addition of 150 and 300 mg/kg of BAs significantly increased the expression levels of zonula occludens-1 (ZO-1) and occludin in the jejunum. Simultaneously 150mg/kg and 300mg/kg BAs increased the total short-chain fatty acids (SCFA) concentrations in the jejunum and cecum(p < 0.05).Supplementation with BAs resulted in a significant increase in the ɑ-diversity of cecal microbiota and a decrease in the abundance of Proteobacteria in the cecum. The addition of 150 mg/kg of BAs significantly reduced the abundance of Bacteroidetes and increased the abundance of Firmicutes. Moreover,Linear discriminant analysis Effect Size analysis (LEfSe) showed that the abundances of bacteria producing SCFA and bile salt hydrolases (BSH) were increased in the BAs-treated group. Furthermore, Spearman's analysis showed that the genus Balutia, which is negatively correlated with visceral fat area, was positively correlated with serum high-density lipoprotein cholesterol (HDL-C), while Clostridium was positively correlated with intestinal VH and VH/CD. In conclusion, BAs can be considered an effective feed additive for geese, as they increased SCFA concentration, improve lipid metabolism and intestinal health by enhancing the intestinal mucosal barrier, improving intestinal morphology, and altering the cecal microbiota structure.

Interactions between intestinal morphology, digestion, inflammatory responses, and gut microbiota of juvenile channel catfish elicited by dietary enzymatic rice protein

The reduction of fishmeal in aquafeeds has been the concern of researchers. Replacing fishmeal with plant proteins affects intestinal function and inflammation, but the interaction between the intestinal responses and gut microbiota remains unclear. In this study, juvenile channel catfish (Ictalurus punctatus) was fed with four diets in which enzymatic rice protein (RP) replaced fishmeal at levels of 0 (FM), 2.5% (RP2.5), 5.0% (RP5.0), and 7.5% (RP7.5) for 8 weeks to solve the problem mentioned above. Quantification of intestinal morphology showed that 2.5% or 5.0% RP significantly increased villus length and goblet cell number, accompanied by higher activities of intestinal trypsin, alkaline phosphatase (AKP), and Na⁺/K⁺-ATPase (NKA) in RP2.5 group (P < 0.05). In contrast, 7.5% RP slightly damaged the intestinal mucosa and significantly reduced the activities of amylase, AKP, and NKA, as well as decreased serum complement 4 (C4) and immunoglobulin M (IgM). Noteworthy, RT-qPCR showed that 2.5% RP significantly down-regulated intestinal mRNA expression level of il8, while up-regulated mif, tlr4, tlr7, tgfβ3, and cldn2. In contrast, 7.5% RP up-regulated the mRNA expression levels of il1β, il8, and mif, while down-regulated cldn3d. Analysis of gut microbiota showed that 2.5% RP increased the relative abundance of Bacteroidetes and significantly activated potential functions of gut microbiota involved in carbohydrate metabolism. The 7.5% RP increased the diversity of the gut microbiota, accompanied by a significant increase in the relative abundance of conditionally pathogenic bacteria such as Vibrio, Serratia, and Aeromonas (classified as Proteobacteria). Notably, Vibrio was the biomarker species with the greatest difference between the FM and RP7.5 groups (genus level). Correlation analysis indicated that Vibrio may affect immunity through the C4 pathway and further lead to gut inflammation and digestive impairment. Taken above, these results indicated that RP could affect intestinal morphology, digestion, and inflammation, and interact with the composition and potential function of gut microbiota. The low RP supplement (2.5%) improved intestinal morphology and digestion, while high supplement (7.5%) disrupted gut microbiota homeostasis, resulting in damage to intestinal mucosa and inflammatory response.