Dietary naringenin reduces high-fat diet-induced liver injury in largemouth bass by regulating intestinal microbiota and activating the ERα/NLRP3 pathway

This study examined the role of intestinal microbiota in berberine (BBR)-mediated glucose (GLU) metabolism regulation in largemouth bass. Four groups of largemouth bass (133.7 ± 1.43g) were fed with control diet, BBR (1g/kg feed) supplemented diet, antibiotic (ATB, 0.9g/kg feed) supplemented diet and BBR + ATB (1g/kg feed +0.9g/kg feed) supplemented diet for 50days. BBR improved growth, decreased the hepatosomatic and visceral weight indices, significantly downregulated the serum total cholesterol and GLU levels, and significantly upregulated the serum total bile acid (TBA) levels. The hepatic hexokinase, pyruvate kinase, GLU-6-phosphatase and glutamic oxalacetic transaminase activities in the largemouth bass were significantly upregulated when compared with those in the control group. The ATB group exhibited significantly decreased final bodyweight, weight gain, specific growth rates and serum TBA levels, and significantly increased hepatosomatic and viscera weight indices, hepatic phosphoenolpyruvate carboxykinase, phosphofructokinase, and pyruvate carboxylase activities, and serum GLU levels. Meanwhile, the BBR + ATB group exhibited significantly decreased final weight, weight gain and specific growth rates, and TBA levels and significantly increased hepatosomatic and viscera weight indices and GLU levels. High-throughput sequencing revealed that compared with those in the control group, the Chao one index and Bacteroidota contents were significantly upregulated and the Firmicutes contents were downregulated in the BBR group. Additionally, the Shannon and Simpson indices and Bacteroidota levels were significantly downregulated, whereas the Firmicutes levels were significantly upregulated in ATB and BBR + ATB groups. The results of in-vitro culture of intestinal microbiota revealed that BBR significantly increased the number of culturable bacteria. The characteristic bacterium in the BBR group was Enterobacter cloacae. Biochemical identification analysis revealed that E. cloacae metabolizes carbohydrates. The size and degree of vacuolation of the hepatocytes in the control, ATB, and ATB + BBR groups were higher than those in the BBR group. Additionally, BBR decreased the number of nuclei at the edges and the distribution of lipids in the liver tissue. Collectively, BBR reduced the blood GLU level and improved GLU metabolism in largemouth bass. Comparative analysis of experiments with ATB and BBR supplementation revealed that BBR regulated GLU metabolism in largemouth bass by modulating intestinal microbiota.

Starch is an inexpensive feed ingredient that has been widely used in fish feed. However, starch utilization by carnivorous fish is limited and excess starch is detrimental to the health of the organism. High starch diets often lead to liver damage, but the effects on the intestine are often overlooked. Therefore, in this study, two isonitrogenous and isolipidic semi-pure diets (NC: 0% α-starch, HC: 22% α-starch) were formulated and fed to largemouth bass (Micropterus salmoides) for 45 days. The effects of the high starch diet on the intestine of largemouth bass were comprehensively investigated by intestinal microbiota, histopathology, ultrastructural pathology, and enzymology analyses. Feeding the HC diet did not affect the growth of largemouth bass during the experimental period. However, the high starch diet led to a reduction in the diversity and abundance of intestinal microbiota in largemouth bass, with a significant increase in the abundance of harmful bacteria (Aeromonas) and a decrease in the abundance of beneficial bacteria (Clostridium, Lactobacillus, and Bifidobacterium). Feeding the HC diet caused the development of enteritis, with goblet cell hyperplasia, epithelial necrosis and detachment and inflammatory cell infiltration, and leading to enlarged apical openings and mitochondrial damage in goblet cells. Long-term feeding of the HC diet inhibited intestinal α-amylase activity. changes in the intestinal microbiota, such as an increase in Aeromonas and a decrease in Clostridium, Lactobacillus, and Bifidobacterium, may be closely related to the development of enteritis. Therefore, adding these beneficial bacteria as probiotics may be an effective way to prevent damage to the intestine of largemouth bass from a high carbohydrate diet. Our results suggest reducing the amount of starch added to the largemouth bass diets. This study provides a reference for protecting the largemouth bass gut during modern intensive culture.

Fermentation of Astragalus by Lactobacillus plantarum and Bacillus coagulans can increase the release of active components and degrade its macromolecular substances. This study investigated the effect of fermentation products (Astragalus + L. plantarum + B. coagulans, ALB) on largemouth bass. We specifically focused on growth performance, serum biochemical indices, intestinal microbial diversity, intestinal enzyme activity, immune gene expression and resistance to infections by Aeromonas hydrophila and largemouth bass ranavirus (LMBRaV). The largemouth bass were divided into five groups based on the amount of ALB added to the feed as following, (1) ALB0 (no ALB, ALB0.5 [0.5% addition of ALB], ALB1 [1% addition of ALB], ALB3 [3% addition of ALB], ALB5 [5% addition of ALB]). The feeding trial spanned 28 days. Comprehensively comparing the feeding results of different ALB concentration, the ALB0.5 group showed the best effect. The ALB0.5 group had significantly increased weight gain rate, alkaline phosphatase, total protein, albumin, digestive enzymes activities of lipase, trypsin and increased intestinal villi and thickness of muscularis propria. And it decreased feed conversion ratio, aspartate aminotransferase and alanine aminotransferase of largemouth bass. Furthermore, the ALB0.5 group improved the richness and diversity of the intestinal microbiota. Increased abundance of dominant phylum and genus in the intestine of largemouth bass included Fusobacteria and Cetobacterium, which promoted the growth and immune performance of largemouth bass. After infection with A. hydrophila and LMBRaV, the survival rates were higher in ALB addition experimental groups than in the ALB0 group, respectively. And the survival rate of ALB0.5 group was higher than other groups. Meanwhile, the ALB added to the feed could regulated the immune gene expression (Mx, IRF-3, TNF-α, IL-1β and IL-10), which also promoted the largemouth bass resistance to disease. In summary, adding 0.5% ALB to the diet of largemouth bass can boost its growth performance, immune genes expression, intestinal health and disease resistance.

Intestinal morphology, immunity and microbiota response to dietary fibers in largemouth bass, Micropterus salmoide

Histologic examination and transcriptome analysis uncovered liver damage in largemouth bass from formulated diets

Elevated environmental ammonia leads to respiratory disorders and metabolic dysfunction in most fish species, and the majority of research has concentrated on fish behavior and gill function. Prior studies have rarely shown the molecular mechanism of the largemouth bass hepatic response to ammonia loading. In this experiment, 120 largemouth bass were exposed to total ammonia nitrogen of 0 mg/L or 13 mg/L for 3 and 7 days, respectively. Histological study indicated that ammonia exposure severely damaged fish liver structure, accompanied by increased serum alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase activity. RT-qPCR results showed that ammonia exposure down-regulated the expression of genes involved in glycogen metabolism, tricarboxylic acid cycle, lipid metabolism, and urea cycle pathways, whereas it up-regulated the expression of genes involved in gluconeogenesis and glutamine synthesis pathways. Thus, ammonia was mainly converted to glutamine in the largemouth bass liver during ammonia stress, which was rarely further used for urea synthesis. Additionally, transcriptome results showed that ammonia exposure also led to the up-regulation of the oxidative phosphorylation pathway and down-regulation of the mitogen-activated protein kinase signaling pathway in the liver of largemouth bass. It is possible that the energy supply of oxidative phosphorylation in the largemouth bass liver was increased during ammonia exposure, which was mediated by the MAPK signaling pathway.

Dietary methionine hydroxy analogue supplementation benefits on growth, intestinal antioxidant status and microbiota in juvenile largemouth bass Micropterus salmoides

Di-(2-ethylhexyl) phthalate exacerbated the toxicity of polystyrene nanoplastics through histological damage and intestinal microbiota dysbiosis in freshwater Micropterus salmoides

This study aimed to investigate the impact of temperature on the intestinal microbiota of largemouth bass using 16S rRNA gene amplicon sequencing, focusing on the under-explored role of abiotic factors in shaping the gut microbial community. Five water temperature groups (20.0±0.2°C, 25.0±0.2°C, 28.0±0.2°C, 31.0±0.2°C, and 35.0±0.2°C) were established, each with three replicates. Significant variations in intestinal bacterial community composition were observed across these conditions. Elevated temperatures (31.0±0.2°C and 35.0±0.2°C) led to an increase in opportunistic pathogens such as OTU180 Vibrio and OTU2015 Vogesella (P<0.05). Species correlation network analysis showed a shift toward more positive relationships among intestinal microbes at higher temperatures (P<0.05). Ecological process analysis highlighted a greater role of ecological drift in microbial community structure at 31.0±0.2°C and 35.0±0.2°C (P<0.05). The study suggests that higher temperatures may predispose largemouth bass to opportunistic pathogens by altering their intestinal microbiota. Effective water temperature management is crucial for largemouth bass aquaculture to mitigate pathogen risks and maintain a balanced intestinal microbiota. This research provides critical insights into the temperature-microbiota relationship and offers practical recommendations for aquaculture practices.

Addition of berberine to formulated feed changes the glucose utilisation, intestinal microbiota and serum metabolites of Largemouth bass (Micropterus salmoides)

Fermented bile acids improved growth performance and intestinal health by altering metabolic profiles and intestinal microbiome in Micropterus salmoides

Microalgae have beneficial effects on the performance of fish as additives and they are becoming a promising alternative to fishmeal as macronutrient ingredients. However, the impact on the fish intestinal microbiome and the function, caused by microalgae as protein sources in diets, remains unclear. This study aimed to determine the composition and potential function of the intestinal microbial community of largemouth bass (Micropterus salmoides) fed diets at five replacement levels (0, 25, 50, 75 and 100%) of fishmeal by Chlorella meal in a basal diet (400 g kg−1) after 8 weeks. The results showed significant decreases in unique amplicon sequence variants in the intestine at the higher levels of fishmeal replacement. At 50% of fishmeal replacement, dietary inclusions of Chlorella meal had no impact on species richness and Shannon diversity and the community structure of the intestinal microbiota. However, high levels of fishmeal replacement (75 and 100%) significantly induced intestinal community disturbance and diversity loss in largemouth bass. Responding to the high fishmeal replacement level, the dominant genus Cetobacterium and Pleslomonas sharply increased and several taxa from Lactobacillus decreased significantly. Functional data predicted by PICRUSt revealed that nutrition-related metabolism was dominant in the intestinal microbiota of fish fed all the five diets, although some potential functions, particularly amino acid and lipid metabolisms, and energy metabolism, were upregulated firstly, and then downregulated in fish fed diets with the increase of dietary Chlorella meal. Meanwhile, certain pathways were not enriched in intestinal microbiome until up to 75% of fishmeal replacement, such as carbohydrate metabolism, and cofactors and vitamins metabolism. To conclude, this study reveals that fishmeal replacement (50%) by Chlorella meal at the level of 237 g kg−1 in diets is feasible for largemouth bass without impairing the microbiome structure and the metabolism function, providing an alternative strategy for evaluating the possibility of fishmeal replacement by microalgae in aquafeeds.

Effects of Ramulus mori oligosaccharides on growth performance, serum physiological and biochemical parameters, and immunomodulation in largemouth bass (Micropterus salmoides)

Coenzyme Q10 (CoQ10) is a powerful antioxidant that is gradually being used in aquafeeds. Here, we examined the influence of oxidized fish oil and CoQ10 supplementation on intestinal microbiota of Micropterus salmoides at different growth stages. Three isonitrogenous and isoenergetic diets were formulated to contain 100% fresh fish oil (FFO), 100% oxidized fish oil (OFO) and OFO + 0.1% CoQ10 (QFO) and were fed to Micropterus salmoides (95 ± 0.60 g) for 70 days. Furthermore, three different growth stages (28-day, 49-day, 70-day) were selected to observe the dynamic changes of intestinal microbiota. The growth performance of fish fed QFO were significantly higher than that of fish fed OFO after a 70-day’s feeding. Intestinal microbial community of Micropterus salmoides was significantly affected by different growth stages more than diets. The abundance of phylum Proteobacteria showed an increasing trend, while the abundance of Firmicutes decreased with increased feeding time. Compared with OFO, diet supplemented with CoQ10 significantly increased the abundance of Firmicutes, and decreased Proteobacteria on the 28- and 70-day of feeding. When fish fed OFO and QFO, Simpson and Shannon indices significantly increased with increased feeding time from 28 to 70 days. Fish fed QFO significantly decreased the value of Bray-Curtis distance than those fed FFO on the 70-day of feeding. Moreover, Bray-Curtis distance showed an increased trend with increased feeding time. Notably, intestinal microbial functional prediction indicated that OFO suppressed amino acid metabolism, while long-term oral administration of CoQ10 could improve amino acid metabolism and detoxification of Micropterus salmoides. This study demonstrated that prolonged application of CoQ10 is needed to produce some beneficial effects to Micropterus salmoides.

BackgroundAdequate level of carbohydrates in aquafeeds help to conserve protein and reduce cost. However, studies have indicated that high-carbohydrate (HC) diet disrupt the homeostasis of the gut–liver axis in largemouth bass, resulting in decreased intestinal acetate and butyrate level.MethodHerein, we had concepted a set of feeding experiment to assess the effects of dietary sodium acetate (SA) and sodium butyrate (SB) on liver health and the intestinal microbiota in largemouth bass fed an HC diet. The experimental design comprised 5 isonitrogenous and isolipidic diets, including LC (9% starch), HC (18% starch), HCSA (18% starch; 2 g/kg SA), HCSB (18% starch; 2 g/kg SB), and HCSASB (18% starch; 1 g/kg SA + 1 g/kg SB). Juvenile largemouth bass with an initial body weight of 7.00 ± 0.20 g were fed on these diets for 56 d.ResultsWe found that dietary SA and SB reduced hepatic triglyceride accumulation by activating autophagy (ATG101, LC3B and TFEB), promoting lipolysis (CPT1α, HSL and AMPKα), and inhibiting adipogenesis (FAS, ACCA, SCD1 and PPARγ). In addition, SA and SB decreased oxidative stress in the liver (CAT, GPX1α and SOD1) by activating the Keap1-Nrf2 pathway. Meanwhile, SA and SB alleviated HC-induced inflammation by downregulating the expression of pro-inflammatory factors (IL-1β, COX2 and Hepcidin1) through the NF-κB pathway. Importantly, SA and SB increased the abundance of bacteria that produced acetic acid and butyrate (Clostridium_sensu_stricto_1). Combined with the KEGG analysis, the results showed that SA and SB enriched carbohydrate metabolism and amino acid metabolism pathways, thereby improving the utilization of carbohydrates. Pearson correlation analysis indicated that growth performance was closely related to hepatic lipid deposition, autophagy, antioxidant capacity, inflammation, and intestinal microbial composition.ConclusionsIn conclusion, dietary SA and SB can reduce hepatic lipid deposition; and alleviate oxidative stress and inflammation in largemouth bass fed on HC diet. These beneficial effects may be due to the altered composition of the gut microbiota caused by SA and SB. The improvement effects of SB were stronger than those associated with SA.