Effects of Shrimp Peptide Hydrolysate on Intestinal Microbiota Restoration and Immune Modulation in Cyclophosphamide-Treated Mice

The gut microbiota is important in regulating host metabolism, maintaining physiology, and protecting immune homeostasis. Gut microbiota dysbiosis affects the development of the gut microenvironment, as well as the onset of various external systemic diseases and metabolic syndromes. Cyclophosphamide (CTX) is a commonly used chemotherapeutic drug that suppresses the host immune system, intestinal mucosa inflammation, and dysbiosis of the intestinal flora. Immunomodulators are necessary to enhance the immune system and prevent homeostasis disbalance and cytotoxicity caused by CTX. In this study, shrimp peptide hydrolysate (SPH) was evaluated for immunomodulation, intestinal integration, and microbiota in CTX-induced immunosuppressed mice. It was observed that SPH would significantly restore goblet cells and intestinal mucosa integrity, modulate the immune system, and increase relative expression of mRNA and tight-junction associated proteins (Occludin, Zo-1, Claudin-1, and Mucin-2). It also improved gut flora and restored the intestinal microbiota ecological balance by removing harmful microbes of various taxonomic groups. This would also increase the immune organs index, serum levels of cytokines (IFN-ϒ, IL1β, TNF-α, IL-6), and immunoglobin levels (IgA, IgM). The Firmicutes/Bacteroidetes proportion was decreased in CTX-induced mice. Finally, SPH would be recommended as a functional food source with a modulatory effect not only on intestinal microbiota, but also as a potential health-promoting immune function regulator.     

Fecal microbiota transplantation ameliorates atherosclerosis in mice with C1q/TNF-related protein 9 genetic deficiency

Despite the strong influence of the gut microbiota on atherosclerosis, a causal relationship between atherosclerosis pathophysiology and gut microbiota is still unverified. This study was performed to determine the impact of the gut microbiota on the pathogenesis of atherosclerosis caused by genetic deficiency. To elucidate the influence of the gut microbiota on atherosclerosis pathogenesis, an atherosclerosis-prone mouse model (C1q/TNF-related protein 9-knockout (CTRP9-KO) mice) was generated. The gut microbial compositions of CTRP9-KO and WT control mice were compared. Fecal microbiota transplantation (FMT) was performed to confirm the association between gut microbial composition and the progression of atherosclerosis. FMT largely affected the gut microbiota in both CTRP9-KO and WT mice, and all transplanted mice acquired the gut microbiotas of the donor mice. Atherosclerotic lesions in the carotid arteries were decreased in transplanted CTRP9-KO mice compared to CTRP9-KO mice prior to transplantation. Conversely, WT mice transplanted with the gut microbiotas of CTRP9-KO mice showed the opposite effect as that of CTRP9-KO mice transplanted with the gut microbiotas of WT mice. Here, we show that CTRP9 gene deficiency is related to the distribution of the gut microbiota in subjects with atherosclerosis. Transplantation of WT microbiotas into CTRP9-KO mice protected against the progression of atherosclerosis. Conversely, the transplantation of CTRP9-KO microbiotas into WT mice promoted the progression of atherosclerosis. Treating atherosclerosis by restoring gut microbial homeostasis may be an effective therapeutic strategy.Subject terms: Atherosclerosis, Experimental models of disease, Mechanisms of disease     

Modeling EBV infection and pathogenesis in new-generation humanized mice

The development of highly immunodeficient mouse strains has allowed the reconstitution of functional human immune system components in mice. New-generation humanized mice generated in this manner have been extensively used for modeling viral infections that are exclusively human tropic. Epstein–Barr virus (EBV)-infected humanized mice reproduce cardinal features of EBV-associated B-cell lymphoproliferative disease and EBV-associated hemophagocytic lymphohistiocytosis (HLH). Erosive arthritis morphologically resembling rheumatoid arthritis (RA) has also been recapitulated in these mice. Low-dose EBV infection of humanized mice results in asymptomatic, persistent infection. Innate immune responses involving natural killer cells, EBV-specific adaptive T-cell responses restricted by human major histocompatibility and EBV-specific antibody responses are also elicited in humanized mice. EBV-associated T-/natural killer cell lymphoproliferative disease, by contrast, can be reproduced in a distinct mouse xenograft model. In this review, recent findings on the recapitulation of human EBV infection and pathogenesis in these mouse models, as well as their application to preclinical studies of experimental anti-EBV therapies, are described.     

Lysozyme-like Protein Produced by Bifidobacterium longum Regulates Human Gut Microbiota Using In Vitro Models

The extracellular secreted protein of Bifidobacterium longum (B. longum) plays an important role in maintaining the homeostasis of the human intestinal microenvironment. However, the mechanism(s) of interaction remain unclear. Lysozyme is a kind of antibacterial peptide. In this study, the amino acid sequence of a lysozyme-like protein of B. longum based on whole-genome data of an isolate from human gut feces was found. We further predicted functional domains from the amino acid sequence, purified the protein, and verified its bioactivity. The growth of some bacteria were significantly delayed by the 020402_LYZ M1 protein. In addition, the gut microbiota was analyzed via high-throughput sequencing of 16S rRNA genes and an in vitro fermentation model, and the fluctuations in the gut microbiota under the treatment of 020402_LYZ M1 protein were characterized. The 020402_LYZ M1 protein affected the composition of human gut microbiota significantly, implying that the protein is able to communicate with intestinal microbes as a regulatory factor.     

Gut microbiota restoration through fecal microbiota transplantation: a new atopic dermatitis therapy

The pathogenesis of atopic dermatitis (AD) involves complex factors, including gut microbiota and immune modulation, which remain poorly understood. The aim of this study was to restore gut microbiota via fecal microbiota transplantation (FMT) to ameliorate AD in mice. FMT was performed using stool from donor mice. The gut microbiota was characterized via 16S rRNA sequencing and analyzed using Quantitative Insights into Microbial Ecology 2 with the DADA2 plugin. Gut metabolite levels were determined by measuring fecal short-chain fatty acid (SCFA) contents. AD-induced allergic responses were evaluated by analyzing blood parameters (IgE levels and eosinophil percentage, eosinophil count, basophil percentage, and monocyte percentage), the levels of Th1 and Th2 cytokines, dermatitis score, and the number of mast cells in the ileum and skin tissues. Calprotectin level was measured to assess gut inflammation after FMT. FMT resulted in the restoration of gut microbiota to the donor state and increases in the levels of SCFAs as gut metabolites. In addition, FMT restored the Th1/Th2 balance, modulated Tregs through gut microbiota, and reduced IgE levels and the numbers of mast cells, eosinophils, and basophils. FMT is associated with restoration of gut microbiota and immunologic balance (Th1/Th2) along with suppression of AD-induced allergic responses and is thus a potential new therapy for AD.Subject terms: Experimental models of disease, Biological therapy     

The Donor-Dependent and Colon-Region-Dependent Metabolism of (+)-Catechin by Colonic Microbiota in the Simulator of the Human Intestinal Microbial Ecosystem

The intestinal absorption of dietary catechins is quite low, resulting in most of them being metabolized by gut microbiota in the colon. It has been hypothesized that microbiota-derived metabolites may be partly responsible for the association between catechin consumption and beneficial cardiometabolic effects. Given the profound differences in gut microbiota composition and microbial load between individuals and across different colon regions, this study examined how microbial (+)-catechin metabolite profiles differ between colon regions and individuals. Batch exploration of the interindividual variability in (+)-catechin microbial metabolism resulted in a stratification based on metabolic efficiency: from the 12 tested donor microbiota, we identified a fast- and a slow-converting microbiota that was subsequently inoculated to SHIME, a dynamic model of the human gut. Monitoring of microbial (+)-catechin metabolites from proximal and distal colon compartments with UHPLC-MS and UPLC-IMS-Q-TOF-MS revealed profound donor-dependent and colon-region-dependent metabolite profiles with 5-(3′,4′-dihydroxyphenyl)-γ-valerolactone being the largest contributor to differences between the fast- and slow-converting microbiota and the distal colon being a more important region for (+)-catechin metabolism than the proximal colon. Our findings may contribute to further understanding the role of the gut microbiota as a determinant of interindividual variation in pharmacokinetics upon (+)-catechin ingestion.     

Biotransformation of Timosaponin BII into Seven Characteristic Metabolites by the Gut Microbiota

Timosaponin BII is one of the most abundant Anemarrhena saponins and is in a phase II clinical trial for the treatment of dementia. However, the pharmacological activity of timosaponin BII does not match its low bioavailability. In this study, we aimed to determine the effects of gut microbiota on timosaponin BII metabolism. We found that intestinal flora had a strong metabolic effect on timosaponin BII by HPLC-MS/MS. At the same time, seven potential metabolites (M1–M7) produced by rat intestinal flora were identified using HPLC/MS-Q-TOF. Among them, three structures identified are reported in gut microbiota for the first time. A comparison of rat liver homogenate and a rat liver microsome incubation system revealed that the metabolic behavior of timosaponin BII was unique to the gut microbiota system. Finally, a quantitative method for the three representative metabolites was established by HPLC-MS/MS, and the temporal relationship among the metabolites was initially clarified. In summary, it is suggested that the metabolic characteristics of gut microbiota may be an important indicator of the pharmacological activity of timosaponin BII, which can be applied to guide its application and clinical use in the future.     

Animal models of acute photodamage: comparisons of anatomic, cellular and molecular responses in C57BL/6J, SKH1 and Balb/c mice

Human cutaneous photodamage is a major medical problem that includes premature aging and fragility of the skin. Nonxenografted animal models have not been comparatively evaluated for how well they resemble the changes seen in human skin. Here, we sought to identify a suitable mouse model that recapitulates key anatomic, cellular and molecular responses observed in human skin during acute UV exposure. Adult females from three strains of mice, C57BL/6J, SKH1 and Balb/c were exposed to UVB and then evaluated 3 or 20 h after the last irradiation. Skin from UVB-exposed C57BL/6J mice showed features resembling human photodamage, including epidermal thickening, infiltration of the dermis with inflammatory cells, induction of tumor necrosis factor-α (TNF-α) mRNA, accumulation of glycosaminoglycans, particularly hyaluronan in the epidermis and loss of collagen. Hairless SKH1 mouse skin responded similarly, but without any induction of TNF-α mRNA or chondroitin sulfate. Irradiated Balb/c mice were the least similar to humans. Our results in C57BL/6J mice and to a lesser extent in SKH1 mice, show cutaneous responses to a course of UVB-irradiation that mirror those seen in human skin. Proper choice of model is critical for investigating cellular and molecular mechanisms of photodamage and photoaging.     

Honeysuckle Berry (Lonicera caerulea L.) Inhibits Lipase Activity and Modulates the Gut Microbiota in High-Fat Diet-Fed Mice

Honeysuckle berry (HB, Lonicera caerulea L.) is an oriental herbal medicine reported to have beneficial effects on metabolic disorders, such as obesity and non-alcoholic fatty liver disease. The fruit part of HB is rich in anthocyanin, a type of polyphenol. Most studies credit the antioxidant and anti-inflammatory properties of HB as the mechanisms of its effectiveness. This study investigated the inhibitory effects of HB on lipase using an in vitro assay and the modulatory effect of HB on gut microbiota in high-fat diet (HFD)-fed mice. HB inhibited pancreatic lipase activity with IC₅₀ values of approximately 0.47 mg/mL. The fecal triglyceride (TG) levels were higher from the HFD of the HB-fed mice than they were for the control mice. Moreover, the fecal microbiota from the HFD of the HB-fed mice had relatively lower Firmicutes and higher Bacteroidetes than that from the HFD-only mice. These results suggest that HB modulates gut microbiota composition, which may contribute to body fat reduction. Hence, HB could present a useful agent for treating metabolic diseases through lower TG uptake and the regulation of gut microflora.     

(20R)-Panaxadiol as a Natural Active Component with Anti-Obesity Effects on ob/ob Mice via Modulating the Gut Microbiota

Obesity is an important cause of diseases such as type 2 diabetes, non-alcoholic fatty liver and atherosclerosis. The use of ingredients extracted from traditional Chinese medicine for weight loss is now receiving more and more attention. Ginseng has been recorded since ancient times for the treatment of diabetes. The (20R)-Panaxadiol (PD) belongs to the ginseng diol type compounds, which are moderately bioavailable and may remain in the intestinal tract for a longer period of time. This study investigated the potential positive effect of PD in ob/ob mice and evaluated its effect against obesity. The ob/ob mice were administered PD for ten weeks. Our study showed that PD could improve obesity, glucose tolerance disorder, as well as gut dysbiosis. Panaxadiol decreased ob/ob mice’s Firmicutes/Bacteroidetes (F/B). Furthermore, 16S rRNA gene sequencing of the fecal microbiota suggested that PD changed the composition of the gut microbiota in ob/ob mice and modulated specific bacteria such as lactobacillus, prevotellace and so on. Moreover, PD improved the intestinal wall integrity. In conclusion, our results suggest that (20R)-Panaxadiol, as an active ingredient of the traditional Chinese medicinal herb ginseng, may improve obesity to some extent via improving gut microbiota     

Ganmaidazao decoction alleviated cognitive impairment on Alzheimer's disease rats by regulating gut microbiota and their corresponding metabolites

Traditional Chinese medicine targeted at gut microbiota has good effects in relieving the clinical manifestation of Alzheimer's disease, and intestinal metabolites are considered as a bridge of communication between the brain-gut axis. In order to explore the molecular mechanism of Ganmaidazao decoction treatment, first, the model rats induced by Aβ25-35 and d-gal were used to test the therapy of Ganmaidazao extract using the Morris Water Maze, Western Blot and Elisa. Then the 16S rDNA gene sequencing of the gut microbiota as well as UPLC-QTOF/MS-based metabolomic analysis of feces were carried out. Last, the relationship between Alzheimer's disease, gut microbiota and metabolites was analyzed. Results showed that the abundance and diversity of gut microbiota were rescued and the changes of fecal metabolites in rats with Alzheimer's disease were reversed after Ganmaidazao decoction administration, which were mainly related to lipid metabolism, steroid hormone metabolism, energy metabolism, amino acid metabolism and bile acid metabolism. After associating with Spearman’s correlation analysis, we concluded that gut microbiota and metabolites were closely related and Ganmaidazao decoction could interfere with the balance of gut microbiota and their corresponding metabolites to exert anti- Alzheimer’s disease effect. Combined with PICRUSt2 functional prediction of gut microbiota and metabolomics results, phenylalanine metabolism has been focused as a key metabolic pathway, and Ganmaidazao decoction can reduce the abnormal accumulation of phenylalanine and phenylpyruvate and promote their metabolism by restoring the activity of phenylalanine hydroxylase. This integrated omics approach has potential roles in understanding the complex mechanisms of Ganmaidazao decoction in treating Alzheimer’s disease.     

Development and Validation of a LC-MS/MS Technique for the Analysis of Short Chain Fatty Acids in Tissues and Biological Fluids without Derivatisation Using Isotope Labelled Internal Standards

The gut microbiota is critical to the maintenance of physiological homeostasis and as such is implicated in a range of diseases such as colon cancer, ulcerative colitis, diabetes, cardiovascular diseases, and neurodegenerative diseases. Short chain fatty acids (SCFAs) are key metabolites produced by the gut microbiota from the fermentation of dietary fibre. Here we present a novel, sensitive, and direct LC-MS/MS technique using isotopically labelled internal standards without derivatisation for the analysis of SCFAs in different biological matrices. The technique has significant advantages over the current widely used techniques based on sample derivatization and GC-MS analysis, including fast and simple sample preparation and short LC runtime (10 min). The technique is specific and sensitive for the quantification of acetate, butyrate, isobutyrate, isovalerate, lactate, propionate and valerate. The limits of detection were all 0.001 mM except for acetate which was 0.003 mM. The calibration curves for all the analytes were linear with correlation coefficients r² > 0.998. The intra- and inter-day precisions in three levels of known concentrations were <12% and <20%, respectively. The quantification accuracy ranged from 92% to 120%. The technique reported here offers a valuable analytical tool for use in studies of SCFA production in the gut and their distribution to host tissues.     

Gut microbiota, diet, and heart disease

Modulation of the gut microbiota is an area of growing interest, particularly for its link to improving and maintaining the systemic health of the host. It has been suggested to have potential to reduce risk factors associated with chronic diseases, such as elevated cholesterol levels in coronary heart disease (CHD). Diets of our evolutionary ancestors were largely based on plant foods, high in dietary fiber and fermentable substrate, and our gut microbiota has evolved against a background of such diets. Therapeutic diets that mimic plant-based diets from the early phases of human evolution may result in drug-like cholesterol reductions. In contrast, typical Western diets low in dietary fiber and fermentable substrate, and high in saturated and trans fatty acids, are likely contributors to the increased need for pharmacological agents for cholesterol reduction. The gut microbiota of those consuming a Western diet are likely underutilized and depleted of metabolic fuels, resulting in a less than optimal gut microbial profile. As a result, this diet is mismatched to our archaic gut microbiota and, therefore, to our genome, which has changed relatively little since humans first appeared. While the exact mechanism by which the gut microbiota may modulate cholesterol levels still remains uncertain, end products of bacterial fermentation, particularly the short chain fatty acids (i.e., propionate), have been suggested as potential candidates. While more research is required to clarify the potential link between gut microbiota and CHD risk reduction, consuming a therapeutic diet rich in plant foods, dietary fiber, and fermentable substrate would be a useful strategy for improving systemic health, possibly by altering the gut microbiota.     

Effect of Gut Microbiota-Derived Metabolites on Immune Checkpoint Inhibitor Therapy: Enemy or Friend?

The human gut is inhabited by hundreds of billions of commensal microbiota that collectively produce thousands of small molecules and metabolites with local and systemic effects on the physiology of the host. Much evidence from preclinical to clinical studies has gradually confirmed that the gut microbiota can regulate anti-tumor immunity and affect the efficacy of cancer immune checkpoint inhibitors (ICIs) therapy. In particular, one of the main modes of gut microbiota regulating anti-tumor immunity is through metabolites, which are small molecules that can be transported in the body and act on local and systemic anti-tumor immune responses to promote ICIs immunotherapy efficacy. We discuss the functions of microbial metabolites in humans, focusing on the effects and mechanisms of microbial metabolites on immunotherapy, and analyze their potential applications as immune adjuvants and therapeutic targets to regulate immunity and enhance ICIs. In summary, this review provides the basis for the rational design of microbiota and microbial metabolite-based strategies of enhancing ICIs.     

Metabolic Labeling of Peptidoglycan with NIR-II Dye Enables In Vivo Imaging of Gut Microbiota

Deepening our understanding of mammalian gut microbiota has been greatly hampered by the lack of a facile, real-time, and in vivo bacterial imaging method. To address this unmet need in microbial visualization, we herein report the development of a second near-infrared (NIR-II)-based method for in vivo imaging of gut bacteria. Using d -propargylglycine in gavage and then click reaction with an azide-containing NIR-II dye, gut microbiota of a donor mouse was strongly labeled with NIR-II fluorescence on their peptidoglycan. The bacteria could be readily visualized in recipient mouse gut with high spatial resolution and deep tissue penetration under NIR irradiation. The NIR-II-based metabolic labeling strategy reported herein, provides, to the best of our knowledge, the first protocol for facile in vivo visualization of gut microbiota within deep tissues, and offers an instrumental tool for deciphering the complex biology of these gut “dark matters”.     

Slimy partners: the mucus barrier and gut microbiome in ulcerative colitis

Ulcerative colitis (UC) is a chronic recurrent intestinal inflammatory disease characterized by high incidence and young onset age. Recently, there have been some interesting findings in the pathogenesis of UC. The mucus barrier, which is composed of a mucin complex rich in O-glycosylation, not only provides nutrients and habitat for intestinal microbes but also orchestrates the taming of germs. In turn, the gut microbiota modulates the production and secretion of mucins and stratification of the mucus layers. Active bidirectional communication between the microbiota and its ‘slimy’ partner, the mucus barrier, seems to be a continually performed concerto, maintaining homeostasis of the gut ecological microenvironment. Any abnormalities may induce a disorder in the gut community, thereby causing inflammatory damage. Our review mainly focuses on the complicated communication between the mucus barrier and gut microbiome to explore a promising new avenue for UC therapy.Subject terms: Glycobiology, Ulcerative colitis     

Anti-Allergic Diarrhea Effect of Diosgenin Occurs via Improving Gut Dysbiosis in a Murine Model of Food Allergy

Although the anti-allergic and prebiotic activities of diosgenin have been reported, the influence of diosgenin on intestinal immune and epithelial cells remains unclear. As the gut microbiota plays an important role in allergic disorders, this study aimed to investigate whether the anti-allergic diarrhea effect of diosgenin occurs via improving gut dysbiosis. In a murine food allergy model, the density of fecal bacterial growth on de Man, Rogossa and Sharpe (MRS) plates was diminished, and growth on reinforced clostridial medium (RCM) and lysogeny broth (LB) agar plates was elevated. However, the oral administration of diosgenin reduced the density of fecal bacteria and ameliorated diarrhea severity. Concordantly, reshaped diversity and an abundance of fecal microbes were observed in some of the diosgenin-treated mice, which showed a milder severity of diarrhea. The relevant fecal strains from the diosgenin-treated mice were defined and cultured with Caco-2 cells and allergen-primed mesenteric lymph node (MLN) cells. These strains exhibited protective effects against the cytokine/chemokine network and allergen-induced T-cell responses to varying degrees. By contrast, diosgenin limitedly regulated cytokine production and even reduced cell viability. Taken together, these findings show that diosgenin per se could not directly modulate the functionality of intestinal epithelial cells and immune cells, and its anti-allergic effect is most likely exerted via improving gut dysbiosis.     

Metabolic Labeling of Peptidoglycan with NIR‐II Dye Enables In Vivo Imaging of Gut Microbiota

Deepening our understanding of mammalian gut microbiota has been greatly hampered by the lack of a facile, real‐time, and in vivo bacterial imaging method. To address this unmet need in microbial visualization, we herein report the development of a second near‐infrared (NIR‐II)‐based method for in vivo imaging of gut bacteria. Using d ‐propargylglycine in gavage and then click reaction with an azide‐containing NIR‐II dye, gut microbiota of a donor mouse was strongly labeled with NIR‐II fluorescence on their peptidoglycan. The bacteria could be readily visualized in recipient mouse gut with high spatial resolution and deep tissue penetration under NIR irradiation. The NIR‐II‐based metabolic labeling strategy reported herein, provides, to the best of our knowledge, the first protocol for facile in vivo visualization of gut microbiota within deep tissues, and offers an instrumental tool for deciphering the complex biology of these gut “dark matters”.     

Lignans and Gut Microbiota: An Interplay Revealing Potential Health Implications

Plant polyphenols are a broad group of bioactive compounds characterized by different chemical and structural properties, low bioavailability, and several in vitro biological activities. Among these compounds, lignans (a non-flavonoid polyphenolic class found in plant foods for human nutrition) have been recently studied as potential modulators of the gut–brain axis. In particular, gut bacterial metabolism is able to convert dietary lignans into therapeutically relevant polyphenols (i.e., enterolignans), such as enterolactone and enterodiol. Enterolignans are characterized by various biologic activities, including tissue-specific estrogen receptor activation, together with anti-inflammatory and apoptotic effects. However, variation in enterolignans production by the gut microbiota is strictly related to both bioaccessibility and bioavailability of lignans through the entire gastrointestinal tract. Therefore, in this review, we summarized the most important dietary source of lignans, exploring the interesting interplay between gut metabolites, gut microbiota, and the so-called gut–brain axis.