Effects of several flavonoids on human gut microbiota and its metabolism by in vitro simulated fermentation.

Introduction: Flavonoids have antiviral, antitumor, anti-inflammatory, and other biological activities. They have high market value and are widely used in food and medicine fields. They also can regulate gut microbiota and promote human health. However, only a few flavonoids have been reported for their regulatory effects on human gut microbiota. Methods: The effects of hesperidin, hesperetin-7-O-glucoside, hesperetin, naringin, prunin, naringenin, rutin, isoquercitrin, and quercetin on gut microbiota structural and metabolic differences in healthy subjects were studied by means of in vitro simulated fermentation technology. Results: Results showed that the nine kinds of flavonoids mentioned above, especially hesperetin-7-O-glucoside, prunin, and isoquercitrin, were found to have more effect on the structure of human gut microbiota, and they could significantly enhance Bifidobacterium (p < 0.05). After 24 h of in vitro simulated fermentation, the relative abundance of intestinal probiotics (e.g., Lactobacillus) was increased by the three flavonoids and rutin. Furthermore, the relative abundance of potential pathogenic bacteria was decreased by the addition of hesperetin-7-O-glucoside, naringin, prunin, rutin, and isoquercitrin (e.g., Lachnoclostridium and Bilophila). Notably, prunin could also markedly decrease the content of H2S, NH3, and short-chain fatty acids. This performance fully demonstrated its broad-spectrum antibacterial activity. Discussion: This study demonstrates that flavonoids can regulate the imbalance of gut microbiota, and some differences in the regulatory effect are observed due to different structures. This work provides a theoretical basis for the wide application of flavonoids for food and medicine.

Transcriptome analysis of the spleen provides insight into the immunoregulation of Scortum barcoo under Streptococcus agalactiae infection.

Jade perch (Scortum barcoo) is a freshwater fish with substantial economic value, which has been widely cultivated all over the world. However, with the intensification and expansion of farming, several bacterial and viral diseases have occurred in jade perch. To understand the immune response of jade perch against Streptococcus agalactiae (Group B Streptococcus, GBS), we performed a histopathological examination and transcriptome sequencing of jade perch spleen after artificial bacterial infection. GBS infection can cause structural changes and even necrosis of the jade perch spleen, which may affect the survival of infected individuals. A total of 144,458 unigenes were obtained through de novo assembly of spleen transcriptome. Among them, 1821 unigenes were identified as DEGs, including 1415 up-regulated and 406 down-regulated unigenes in the infection group. Moreover, the analysis of GO and KEGG revealed that many GO terms and pathways were involved in the host immune response, such as Toll-like receptor signaling pathway, Cytokine-cytokine receptor interaction, and TNF signaling pathway. In addition, according to transcriptome data and qRT-PCR analysis, the expression levels of many cytokines that participate in the inflammatory response changed a lot after GBS infection. Overall, this transcriptomic analysis provided valuable information for studying the immune response of jade perch against bacterial infection.

Homologous Expression and Characterization of α-L-rhamnosidase from Aspergillus niger for the Transformation of Flavonoids.

Aspergillus niger has been used for homologous and heterologous expressions of many protein products. In this study, the α-L-rhamnosidase from A. niger (Rha-N1, GenBank XP_001389086.1) was homologously expressed in A. niger 3.350 by Agrobacterium tumefaciens-mediated transformation. The enzyme activity of Rha-N1 was 0.658 U/mL, which was obtained by cultivation of engineered A. niger in a 5-L bioreactor. Rha-N1 was purified by affinity chromatography and characterized. The optimum temperature and optimum pH for Rha-N1 were 60 °C and 4.5, respectively. Enzyme activity was promoted by Al3+, Li+, Mg2+, and Ba2+ and was inhibited by Mn2+, Fe3+, Ca2+, Cu2+, and organic solvents. The result indicated that rutin was the most suitable substrate for Rha-N1 by comparison with the other two flavonoid substrates hesperidin and naringin. The transformed products of isoquercitrin, hesperetin-7-O-glucoside, and prunin were identified by LC-MS and 1H-NMR.

Comparative Metabolomics and Proteomics Reveal Vibrio parahaemolyticus Targets Hypoxia-Related Signaling Pathways of Takifugu obscurus.

Coronavirus disease 2019 (COVID-19) raises the issue of how hypoxia destroys normal physiological function and host immunity against pathogens. However, there are few or no comprehensive omics studies on this effect. From an evolutionary perspective, animals living in complex and changeable marine environments might develop signaling pathways to address bacterial threats under hypoxia. In this study, the ancient genomic model animal Takifugu obscurus and widespread Vibrio parahaemolyticus were utilized to study the effect. T. obscurus was challenged by V. parahaemolyticus or (and) exposed to hypoxia. The effects of hypoxia and infection were identified, and a theoretical model of the host critical signaling pathway in response to hypoxia and infection was defined by methods of comparative metabolomics and proteomics on the entire liver. The changing trends of some differential metabolites and proteins under hypoxia, infection or double stressors were consistent. The model includes transforming growth factor-ß1 (TGF-ß1), hypoxia-inducible factor-1α (HIF-1α), and epidermal growth factor (EGF) signaling pathways, and the consistent changing trends indicated that the host liver tended toward cell proliferation. Hypoxia and infection caused tissue damage and fibrosis in the portal area of the liver, which may be related to TGF-ß1 signal transduction. We propose that LRG (leucine-rich alpha-2-glycoprotein) is widely involved in the transition of the TGF-ß1/Smad signaling pathway in response to hypoxia and pathogenic infection in vertebrates as a conserved molecule.