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Hyperlipidemia, characterized by elevated serum lipid concentrations resulting from lipid metabolism dysfunction, represents a prevalent global health concern. Ginsenoside Rb1, compound K (CK), and 20(S)-protopanaxadiol (PPD), bioactive constituents derived from Panax ginseng, have shown promise in mitigating lipid metabolism disorders. However, the comparative efficacy and underlying mechanisms of these compounds in hyperlipidemia prevention remain inadequately explored. This study investigates the impact of ginsenoside Rb1, CK, and PPD supplementation on hyperlipidemia in rats induced by a high-fat diet. Our findings demonstrate that ginsenoside Rb1 significantly decreased body weight and body weight gain, ameliorated hepatic steatosis, and improved dyslipidemia in HFD-fed rats, outperforming CK and PPD. Moreover, ginsenoside Rb1, CK, and PPD distinctly modified gut microbiota composition and function. Ginsenoside Rb1 increased the relative abundance of Blautia and Eubacterium, while PPD elevated Akkermansia levels. Both CK and PPD increased Prevotella and Bacteroides, whereas Clostridium-sensu-stricto and Lactobacillus were reduced following treatment with all three compounds. Notably, only ginsenoside Rb1 enhanced lipid metabolism by modulating the PPARγ/ACC/FAS signaling pathway and promoting fatty acid β-oxidation. Additionally, all three ginsenosides markedly improved bile acid enterohepatic circulation via the FXR/CYP7A1 pathway, reducing hepatic and serum total bile acids and modulating bile acid pool composition by decreasing primary/unconjugated bile acids (CA, CDCA, and β-MCA) and increasing conjugated bile acids (TCDCA, GCDCA, GDCA, and TUDCA), correlated with gut microbiota changes. In conclusion, our results suggest that ginsenoside Rb1, CK, and PPD supplementation offer promising prebiotic interventions for managing HFD-induced hyperlipidemia in rats, with ginsenoside Rb1 demonstrating superior efficacy. [ABSTRACT FROM AUTHOR]

Background: Hosts, parasites, and microbiota interact with each other, forming a complex ecosystem. Alterations to the microbial structure have been observed in various enteric parasitic infections (e.g. parasitic protists and helminths). Interestingly, some parasites are associated with healthy gut microbiota linked to the intestinal eubiosis state. So the changes in bacteria and metabolites induced by parasite infection may offer benefits to the host, including protection from other parasitesand promotion of intestinal health. The only ciliate known to inhabit the hindgut of grass carp, Balantidium ctenopharyngodoni, does not cause obvious damage to the intestinal mucosa. To date, its impact on intestinal microbiota composition remains unknown. In this study, we investigated the microbial composition in the hindgut of grass carp infected with B. ctenopharyngodoni, as well as the changes of metabolites in intestinal contents resulting from infection. Results: Colonization by B. ctenopharyngodoni was associated with an increase in bacterial diversity, a higher relative abundance of Clostridium, and a lower abundance of Enterobacteriaceae. The family Aeromonadaceae and the genus Citrobacter had significantly lower relative abundance in infected fish. Additionally, grass carp infected with B. ctenopharyngodoni exhibited a significant increase in creatine content in the hindgut. This suggested that the presence of B. ctenopharyngodoni may improve intestinal health through changes in microbiota and metabolites. Conclusions: We found that grass carp infected with B. ctenopharyngodoni exhibit a healthy microbiota with an increased bacterial diversity. The results suggested that B. ctenopharyngodoni reshaped the composition of hindgut microbiota similarly to other protists with low pathogenicity. The shifts in the microbiota and metabolites during the colonization and proliferation of B. ctenopharyngodoni indicated that it may provide positive effects in the hindgut of grass carp. [ABSTRACT FROM AUTHOR]

Lipids are an essential component of living beings and an important group of nutrients. As the gut microbiota plays important roles in the intestinal absorption and extraintestinal metabolism of dietary lipids, the current review addresses the recent progress regarding the interactions between the gut microbiota and lipid metabolism in aquatic animals, with a focus on fish. We discuss in detail how dietary lipid sources and content affect the composition of the gut microbiome and the mechanism by which the gut microbiota affects the lipid metabolism of the host. This interaction is largely mediated via microbial lipases, short‐chain fatty acids and the gut‐liver axis. The latter refers to the metabolism of biliary salts and acids, the regulation of their synthesis by gut microbes and their impact on the lipid metabolism. Finally, we briefly discuss how probiotic supplementation modulates the host's microbiome, and how probiotics have a beneficial effect on health and welfare of farmed aquatic animals. Although the influence of intestinal microbiota on lipid metabolism has been explored before, further research is needed to profoundly investigate the molecular mechanisms by which microbial metabolites (SCFAs and bile acids) induce lipid metabolism. [ABSTRACT FROM AUTHOR]

The intestinal microbiota contributes to energy metabolism, but the molecular mechanisms involved remain less clear. Bacteria of the genus Bacillus regulate lipid metabolism in the host and are thus commonly used as beneficial probiotic supplements. In the present study, Bacillus licheniformis FA6 was selected to assess its role in modulating lipid metabolism of zebrafish (Danio rerio). Combining 16S rRNA high-throughput sequencing, micro-CT scan, metabolic parameters measurement, and gene expression analysis, we demonstrated that B. licheniformis FA6 changed the gut microbiota composition of zebrafish and increased both the Firmicutes/Bacteroidetes ratio and lipid accumulation. In terms of metabolites, B. licheniformis FA6 appeared to promote acetate production, which increased acetyl-CoA levels and promoted lipid synthesis in the liver. In contrast, addition of B. licheniformis lowered carnitine levels, which in turn reduced fatty acid oxidation in the liver. At a molecular level, B. licheniformis FA6 upregulated key genes regulating de novo fatty acid synthesis and downregulated genes encoding key rate-limiting enzymes of fatty acid β-oxidation, thereby promoting lipid synthesis and reducing fatty acid oxidation. Generally, our results reveal that B. licheniformis FA6 promotes lipid accumulation in zebrafish through improving lipid synthesis and reducing β-oxidation. [ABSTRACT FROM AUTHOR]

Gut microbiota plays an important role in metabolic homeostasis. Previous studies demonstrated that ginsenoside Rb1 might improve obesity-induced metabolic disorders through regulating glucose and lipid metabolism in the liver and adipose tissues. Due to low bioavailability and enrichment in the intestinal tract of Rb1, we hypothesized that modulation of the gut microbiota might account for its pharmacological effects as well. Here, we show that oral administration of Rb1 significantly decreased serum LDL-c, TG, insulin, and insulin resistance index (HOMA-IR) in mice with a high-fat diet (HFD). Dynamic profiling of the gut microbiota showed that this metabolic improvement was accompanied by restoring of relative abundance of some key bacterial genera. In addition, the free fatty acids profiles in feces were significantly different between the HFD-fed mice with or without Rb1. The content of eight long-chain fatty acids (LCFAs) was significantly increased in mice with Rb1, which was positively correlated with the increase of Akkermansia and Parasuttereller , and negatively correlated with the decrease of Oscillibacter and Intestinimonas. Among these eight increased LCFAs, eicosapentaenoic acid (EPA), octadecenoic acids, and myristic acid were positively correlated with metabolic improvement. Furthermore, the colonic expression of the free fatty acid receptors 4 (Ffar4) gene was significantly upregulated after Rb1 treatment, in response to a notable increase of LCFA in feces. These findings suggested that Rb1 likely modulated the gut microbiota and intestinal free fatty acids profiles, which should be beneficial for the improvement of metabolic disorders in HFD-fed mice. This study provides a novel mechanism of Rb1 for the treatment of metabolic disorders induced by obesity, which may provide a therapeutic avenue for the development of new nutraceutical-based remedies for treating metabolic diseases, such as hyperlipidemia, insulin resistance, and type 2 diabetes. [ABSTRACT FROM AUTHOR]

To determine the impacts of housefly larvae (Musca domestica) on the Chinese soft‐shelled turtle (Pelodiscus sinensis), sixty‐three turtles with an initial body weight of 65.33±7.35 g were randomly distributed into nine 120‐L tanks to three diet groups (three replicates each group), each group containing 21 turtles: basal diet every day (PBD), housefly larvae fed once weekly (PFL7, six‐day basal diet and one‐day housefly larvae), housefly larvae fed every third day (PFL3, two‐day basal diet and one‐day housefly larvae). We investigated their growth performance, immunity and intestinal microbiota. We found that the weight gain and specific growth rate were significantly higher in the larvae‐supplemented groups than in the PBD group (p < 0.05), whereas the lipid accumulation in the liver was lower. Expression levels of IgD and IgM (immune genes) were significantly increased in the gut samples of PFL7 group (p < 0.05). Meanwhile, the larvae supplementation influenced the composition and diversity of gut microbiota of turtles; the abundance of Bacillus and Bacteroides increased significantly. PICRUSt functional prediction indicated that both larvae‐supplemented groups exhibited upregulation of genes involved in lipid metabolism and carbohydrate metabolism, and downregulation of genes associated with infectious and cardiovascular diseases. In conclusion, dietary supplementation of housefly larvae had positive effects on the growth, liver health, immunity and intestinal microbiota of P. sinensis, suggesting that housefly larvae are a promising dietary supplement for the Chinese soft‐shelled turtle. [ABSTRACT FROM AUTHOR]

In mammals, bile acid (BA) concentrations are regulated largely by the gut microbiota, and a study has shown that some metabolic responses to the gut microbiota are conserved between zebrafish and mice. However, it remains unknown whether the influence of specific intestinal microbes on BA metabolism is conserved between higher and lower vertebrates (i.e., mammals and fish). In the present study, Citrobacter freundii GC01 isolated from the grass carp (Ctenopharyngodon idella) intestine was supplemented to the fish and mice feed. We found the changes in the bile acid profile, especially significant changes in secondary BAs in both grass carp and mice fed on C. freundii. Also, lipid metabolism was significantly affected by C. freundii. Analysis of liver transcriptome sequencing data and validation by RT-qPCR revealed that the CYP7A1 gene was significantly up-regulated in both grass carp and mice. In addition, the overexpression of HNF4B from grass carp resulted in a significant increase in the expression level of CYP7A1. Generally, our results suggest that the metabolism of BAs by intestinal microbiota is conserved across vertebrates. Furthermore, specific intestinal bacteria may regulate the bile salt synthesis through CYP7A1 and that HNF4B might be an important regulator of BA metabolism in fish. [ABSTRACT FROM AUTHOR]

Housefly larvae are widely used in livestock breeding industry as a functional feed additive with immunostimulant properties, but their effects as dietary additive are poorly understood in aquatic animals. We conducted an eight‐week rearing experiment to determine the effects of housefly larvae (complete) on growth performance, immunity and intestinal microbiota in swamp eel (Monopterus albus). Dietary treatments were as follows: BD (control group, fed a basal diet), FL7 (fly larvae supplemented once weekly, i.e., 6‐day basal diet, 1‐day larvae) and FL3 (larvae supplemented every third day, i.e., 2‐day basal diet, 1‐day larvae). The final body weight (FBW) and weight gain (WG) of the FL3 group significantly (p <.05) increased. Hepatosomatic index (HSI) and malondialdehyde (MDA) concentration significantly decreased in FL3 and FL7 groups. The expression of immune‐related genes was also influenced by the fly larvae. Aeromonas hydrophila challenge experiment produced higher survival rates in the FL3 (75%) and FL7 (37.5%) groups. Fly larvae also affected the composition of gut microbiota: the abundance of Bacteroides increased, and Pseudomonas decreased, in the treatment groups. Dietary supplementation of housefly larvae has positive effects on the growth and immunity of swamp eel, and we suggest supplementing housefly larvae every third day. [ABSTRACT FROM AUTHOR]

Background: Parasitic protozoans, helminths, alter the gut microbiota in mammals, yet little is known about the influence of intestinal cestodes on gut microbiota in fish. In the present study, the composition and diversity of the hindgut microbiota were determined in the intestine of common carp (Cyprinus carpio) infected with two tapeworm species, Khawia japonensis and Atractolytocestus tenuicollis. Results: The intestine contained a core microbiota composed of Proteobacteria, Fusobacteria and Tenericutes. Infection with the two cestode species had no significant effect on the microbial diversity and richness, but it altered the microbial composition at the genus level. PCoA analysis indicated that microbial communities in the infected and uninfected common carp could not be distinguished from each other. However, a Mantel test indicated that the abundance of K. japonensis was significantly correlated with the microbial composition (P = 0.015), while the abundance of A. tenuicollis was not (P = 0.954). According to Pearsonʼs correlation analysis, the abundance of K. japonensis exhibited an extremely significant (P < 0.001) positive correlation with the following gut microbiota taxa: Epulopiscium, U114, Bacteroides, Clostridium and Peptostreptococcaceae (0.8< r < 0.9); and a significant (P < 0.05) correlation with Enterobacteriaceae, Micrococcaceae, Rummeliibacillus, Lysinibacillusboronitolerans, Veillonellaceae, Oxalobacteraceae, Aeromonadaceae (negative), Marinibacillus and Chitinilyticum (0.4< r < 0.7). Conclusions: These results suggest that the composition of gut microbiota was somewhat affected by the K. japonensis infection. Additionally, increased ratios of pathogenic bacteria (Lawsonia and Plesiomonas) were also associated with the K. japonensis infection, which may therefore increase the likelihood of disease. [ABSTRACT FROM AUTHOR]

Diet is known to influence intestinal microbiota in fish, but the specifics of these impacts are still poorly understood. Different protein/fibre ratio diets may result in differing structures and activities of gut microbiota. We examined the hindgut microbiome of grass carp ( Ctenopharyngodon idellus) fed three different diets: fish meal ( FM, high protein - low fibre), Sudan grass ( SG, high fibre - low protein) and compound feed ( CF, intermediate). Microbial profiles of fish fed on FM were significantly different from profiles of fish fed CF and SG ( F = 18.85, p < .01). Cetobacterium, known to be positively associated with protein digestion, was the dominant microbial group in FM samples (approximately 75.7%), while Lachnospiraceae and Erysipelotrichaceae, thought to be involved in fermentation of plant polysaccharides, were dominant in CF and SG samples (46.8% and 42.9% respectively). Network analyses indicated that the abundance of Lachnospiraceae and Erysipelotrichaceae was in a significantly positive correlation ( r = .895, p = .001). Short-chain fatty acid ( SCFA) levels may indicate that the digestibility of diet by microbiota in the grass carp gut decreased from FM to SG ( FM> CF> SG). Overall low SCFA levels indicate that hindgut fermentation probably provides a low proportion of energy requirements in grass carp. [ABSTRACT FROM AUTHOR]

To elucidate the influence of different diet on the intestinal microbe and bile acids, we characterized the microbiota and bile acids in the hindgut content of grass carp fed on formula feed ( FF group) or Sudan grass ( SG group). Fusobacteria and Proteobacteria were significantly more represented in FF group than in SG group whereas Bacteroidetes was significantly more abundant in SG group than in FF group. Simpson diversity was significantly higher in FF group than in SG group ( t = 2.33, P < 0.05). Chenodeoxycholic acid ( CDCA) was the most abundant primary bile acid in the two groups, with average concentrations of 1.03 ± 0.62 and 4.44 ± 1.80 ng mg−1 in SG and FF group respectively. The most abundant secondary bile acid was deoxycholic acid ( DCA) in SG group and ursodeoxycholic acid ( UDCA) in FF group, with average concentrations of 0.17 ± 0.06 and 2.67 ± 0.88 ng mg−1 respectively. UDCA is significantly more abundant in FF group than in SG group, and the total bile acids were higher in FF group than in SG group. Cetobacterium and Fusobacteriaceae U114 were significantly related with the concentrations of CDCA ( r = 0.85, P < 0.05 and r = 0.82, P < 0.05 respectively) and UDCA ( r = 0.92, P < 0.01 and r = 0.92, P < 0.01 respectively). However, Bacteroides was negatively related with the concentration of UDCA ( r = −0.67, P < 0.05). Overall, there existed certain relationship between the intestinal microbes and the faecal bile acids, and they were both influenced by the diet. [ABSTRACT FROM AUTHOR]

Traditional culture-based technique and 16S rDNA sequencing method were used to investigate the mucosa-associated autochthonous microbiota of grass carp ( Ctenopharyngodon idellus). Twenty-one phylotypes were detected from culturable microbiota, with Aeromonas, Shewanella, Lactococcus, Serratia, Brevibacillus, Delftia, Pseudomonas, Pantoea, Enterobacter, Buttiauxella and Yersinia as their closest relatives. Genomic DNA was directly extracted from the gut mucosa of C. idellus originating from six different geographical regions, and used to generate 609 random bacterial clones from six clone libraries and 99 archaeal clones from one library, which were grouped into 67 bacterial and four archaeal phylotypes. Sequence analysis revealed that the intestinal mucosa harboured a diversified bacterial microbiota, where Proteobacteria, Firmicutes and Bacteroidetes were dominant, followed by Actinobacteria, Verrucomicrobia and Deinococcus- Thermus. The autochthonous bacterial communities in the gut mucosa of fish from different aquatic environments were not similar (Cs < 0.80), but γ- Proteobacteria was a common bacterial class. In comparison to bacterial communities, the archaeal community obtained from one library consisted of Crenarchaeota and Euryarchaeota. These results demonstrate that molecular methods facilitate culture-independent studies, and that fish gut mucosa harbours a larger bacterial diversity than previously recognized. The grass carp intestinal habitat selects for specific bacterial taxa despite pronounced differences in host environments. [ABSTRACT FROM AUTHOR]

The intestinal microbiota has received increasing attention, as it influences growth, feed conversion, epithelial development, immunity as well as the intrusion of pathogenic microorganisms in the intestinal tract. In this study, pyrosequencing was used to explore the bacterial community of the intestine in gibel carp ( Carassius auratus gibelio), and the origin of these microorganisms. The results disclosed great bacterial diversities in the carp intestines and cultured environments. The gibel carp harbored characteristic intestinal microbiota, where Proteobacteria were predominant, followed by Firmicutes. The analysis on the 10 most abundant bacterial operational taxonomic units (OTUs) revealed a majority of Firmicutes in the intestinal content (by decreasing order: Veilonella sp., Lachnospiraceae, Lactobacillales, Streptococcus sp., and Lactobacillus sp.). The second most abundant OTU was Rothia sp. (Actinobacteria). The most likely potential probiotics ( Lactobacillus sp., and Bacillus sp.) and opportunists ( Aeromonas sp., and Acinetobacter sp.) were not much abundant. Bacterial community comparisons showed that the intestinal community was closely related to that of the sediment, indicating the importance of sediment as source of gut bacteria in gibel carp. However, 37.95 % of the OTUs detected in feed were retrieved in the intestine, suggesting that food may influence markedly the microbiota of gibel carp, and therefore may be exploited for oral administration of probiotics. [ABSTRACT FROM AUTHOR]

Abstract Gut microbiota and its metabolites affect lipid metabolism and liver health. Grass carp (Ctenopharyngodon idellus) often suffers from functional disorders of liver and gallbladder, which is usually accompanied by accumulation of lipids in the liver. Here we studied liver transcriptome and microbial fluctuation in the gut in response to dietary lithocholic acid (LCA; a metabolite of gut microbiota) supplementation in grass carp. A total of 1802 differentially expressed genes (DEGs) were identified between LCA and Control groups according to the liver transcriptome analysis. Of these DEGs, 8 nonalcoholic fatty liver disease-related genes were all upregulated, and 11 of 12 cancer related genes were upregulated in the LCA group. We also found significantly upregulated bile acid receptor, hepatocyte nuclear factor 4-beta (HNF4B), in the LCA group. The red oil O staining of liver showed a higher abundance of lipid droplets in the LCA group. LCA also changed the composition of gut microbiota, with increasing proportion of Proteobacteria and Firmicutes, whereas Fusobacteria decreased. Co-occurrence between DEGs and microbial taxa was mainly identified between signal transduction and genetic information processing-related genes and Proteobacteria and Firmicutes taxa. Overall, our results elucidate the effects of LCA on liver and gut microbiota in fish, and suggest a novel pattern of bile acid feedback in grass carp. These results contribute to our understanding of the interplay between gut microbiota and liver diseases in fish, and offer insights into putative treatments of liver diseases in grass carp. Highlights • The effects of secondary BAs on the regulation of metabolic pathways and physiology in lower vertebrates, e.g. fish, remain poorly understood, here we uncovered that lithocholic acid (LCA) could disturb lipid metabolism in the liver of grass carp and influence composition of its gut micriobiota. • We also found significantly upregulated bile acid receptor, hepatocyte nuclear factor 4-beta (HNF4B) in the LCA fed group, which suggested a novel pattern of bile acid feedback in grass carp. • Our results contribute to our understanding of the interplay between gut microbiota and liver diseases in fish, and offer insights into putative treatments of liver diseases in grass carp. [ABSTRACT FROM AUTHOR]

There are indications that the intestinal microbiota, bile acids, lipid metabolism, and host genotype may all be interconnected, but their interrelationships are still only partially understood. In the present study, we designed three feeding trials and used gibel carp (Carassius auratus gibelio) as a model to investigate the interactions among all of the above parameters. In trial 1, we used wild-type (WT) and heterozygous pik3r1 -deficient (P85+/−) fish (each n = 15) and found that the composition and structure of gut microbiota significantly differed between the two groups. The WT group exhibited a lower intestinal content of bile acids and increased physiological and histological parameters associated with obesity. Citrobacter freundii was significantly correlated with bile acid content. In trial 2, we supplemented two different levels of C. freundii GC01 strain to the WT fish diet: 106 (C6) and 109 (C9) cfu/kg (all n = 24). Experimental groups had lower obesity indices, but higher growth parameters, and bile acid content. As cholic acid was the most abundant bile acid in the gut of gibel carp, in trial 3 we supplemented it to the fish feed: the experimental group had lower obesity indices. In summary, the P85+/− genotype restructured intestinal microbiota and increased the abundance of C. freundii. This triggered a metabolic cascade: gut microbiota modulation affected the bile acid content, which then affected the lipid metabolism, and thereby obesity indices in fish. The intriguing observation that Citrobacter freundii GC01 appears to improve feed utilization in gibel carp, while simultaneously reducing lipid accumulation, deserves further studies aimed at potential application in aquaculture. [Display omitted] • Our experiment has demonstrated that the host's genotype restructures the gut microbiome and regulates fat metabolism in fish. • We find a metabolic cascade: gut microbiota modulation affected bile acid content – which affected lipid metabolism in fish. • Our results indicate that certain bacterial strain may improve feed utilization and growth parameters, while reducing obesity [ABSTRACT FROM AUTHOR]

The effect of Citrobacter freundii , an opportunistic pathogen of fish, on the gut microbiota and immune responses in fish remains unknown. We fed grass carp (Ctenopharyngodon idellus) with two different concentrations of this bacterium (experimental Low and High groups, plus Control group). No signs of acute inflammatory response were found in either of the experimental groups using the intestinal HE staining method, but the number of intestinal goblet cells was much higher in the High group. Furthermore, we found that feeding C. freundii significantly decreased the alpha diversity and altered beta diversity of gut microbiota in both groups, and significantly promoted the relative abundance of Enterobacteriales, Pasteurellales, Neisseriales and Citrobacter in the High group. Spleen transcriptome showed that the expression pattern of immune system-related genes varied significantly between the Control group and High group. Several immunity-related pathways and two infectious diseases-related pathways were significantly enriched in the High group. Many complement system genes, including c3 , c4 , c5 , c7 , c8a , c8b and c1s , were also up-regulated in the High group. Overall, our results indicate that C. freundii did not trigger acute intestinal inflammation, but it changed the diversity and population structure of gut microbiota, and triggered the host's innate mucosal immune system. The enrichment of two infectious diseases-related pathways also suggested a higher risk of infection in the High group. These results contribute to our understanding of the effects of opportunistic fish pathogens on gut microbiota and host's immune responses. • We supplemented Citrobacter freundii GC01 to the diet of grass carp and found it significantly increased the number of intestinal goblet cells. • C. freundii GC01 decreased the alpha diversity and altered the beta diversity of the gut microbiota, as well as up-regulated the expression of seven complement system-related genes in the spleen of grass carp. • Our results suggest that intestinal immunity response can be regulated by gut microbiota, which might be potential application in aquaculture. [ABSTRACT FROM AUTHOR]