Serine Alleviates Dextran Sulfate Sodium-Induced Colitis and Regulates the Gut Microbiota in Mice

Serine deamination by human serine racemase synergizes with antibiotics to curtail the replication of Chlamydia trachomatis

The obligate intracellular bacterium, Chlamydia trachomatis, has evolved to depend on its human host for many metabolites, including most amino acids and three of the four nucleotides. Given this, it is not surprising that depletion of a single amino acid in the host cell growth medium blocks chlamydial replication. Paradoxically, supra-normal levels of some amino acids also block productive replication of Chlamydia. Here, we have determined how elevated serine levels, generated by exogenous supplementation, impede chlamydial inclusion development and reduce the generation of infectious progeny. Our findings reveal that human serine racemase, which is broadly expressed in multiple tissues, potentiates the anti-chlamydial effect of elevated serine concentrations. In addition to reversibly converting l-serine to d-serine, serine racemase also deaminates serine via β-elimination. We have determined that d-serine does not directly impact Chlamydia; rather, ammonia generated by serine deamination limits the productive chlamydial replication. Our findings imply that ammonia produced within host cells can traverse the chlamydial inclusion membrane. Further, this property of serine deaminase can be exploited to sensitize Chlamydia to concentrations of doxycycline that are otherwise not bactericidal. Because exogenously elevated levels of serine can be tolerated over extended periods, the broad expression pattern of serine racemase indicates it to be a host enzyme whose activity can be directed against multiple intracellular bacterial pathogens. From a therapeutic perspective, demonstrating host metabolism can be skewed to generate an anti-bacterial metabolite that synergizes with antibiotics, we believe our results provide a new approach to target intracellular pathogens.

Cucurbitacin E Alleviates Colonic Barrier Function Impairment and Inflammation Response and Improves Microbial Composition on Experimental Colitis Models

Purpose

Cucurbitacins, which are found in a variety of medicinal plants, vegetables and fruits, were known for their diverse pharmacological and biological activities, including anticancer, anti-oxidative and anti-inflammatory effects. Cucurbitacin E, one of the major cucurbitacins, was recently proved to inhibit inflammatory response.

Methods

To explore the therapeutic effects of cucurbitacin E on colitis and the underlying mechanisms, male mice drunk water containing 2.5% dextran sulfate sodium (DSS) to establish colitis model and administrated with cucurbitacin E during and after DSS treatment. The disease activity index was scored and colonic histological damage was observed. Intestinal tight junction and inflammatory response were determined. 16S rRNA and transcriptome sequencing were performed to analyze gut microbiota composition and gene expression, respectively.

Results

We found that cucurbitacin E alleviated DSS-induced body weight loss and impaired colonic morphology. Cucurbitacin E decreased the expression of inflammatory cytokines and cell apoptosis, and maintained barrier function. Additionally, cucurbitacin E retrieved DSS-induced alterations in the bacterial community composition. Furthermore, a variety of differentially expressed genes (DEGs) caused by cucurbitacin E were enriched in several pathways including the NFκB and TNF signaling pathways as well as in Th17 cell differentiation. There was a close relationship between DEGs and bacteria such as Escherichia-Shigella and Muribaculaceae.

Conclusion

Our results revealed that cucurbitacin E may exert protective effects on colitis via modulating inflammatory response, microbiota composition and host gene expression. Our study supports the therapeutic potential of cucurbitacin E in colitis and indicates that gut microbes are potentially therapeutic targets.

Bacteroides fragilis aggravates high-fat diet-induced non-alcoholic fatty liver disease by regulating lipid metabolism and remodeling gut microbiota

Gut microbiota dysbiosis is a prominent determinant that significantly contributes to the disruption of lipid metabolism. Consequently, it is essential to the occurrence and development of non-alcoholic fatty liver disease (NAFLD). Nevertheless, the connection between diet and symbiotic gut microbiota in the progression of NAFLD remains uncertain. The purpose of this study was to explore the role of supplementing commensal Bacteroides fragilis (B. fragilis) on lipid metabolism, gut microbiota, and metabolites in high-fat diet (HFD)-fed mice, elucidating the impact of gut microbiota and metabolites on the development of NAFLD. Our study revealed that supplementation with B. fragilis exacerbated both weight gain and obesity in mice. B. fragilis exacerbated blood glucose levels and liver dysfunction in mice. Furthermore, an increase in liver lipid accumulation and the upregulation of genes correlated with lipid metabolism were observed in mice. Under an HFD, supplementation of commensal B. fragilis resulted in alterations in the gut microbiota, notably a significant increase in Desulfovibrionaceae, which led to elevated endotoxin levels and thereby influenced the progression of NAFLD. It was interesting that the simultaneous examination of gut microbiota metabolites revealed a more pronounced impact of diet on short-chain fatty acids. This study represented the pioneering investigation into the impact of B. fragilis on NAFLD. Our findings demonstrated that B. fragilis induced dysregulation in the intestinal microbiota, leading to elevated levels of lipopolysaccharide and dysfunction in glucose and lipid metabolism, thereby exacerbating NAFLD.IMPORTANCESome intestinal symbiotic microbes are involved in the occurrence of the metabolic disorders. Our study investigated the impact of supplementing commensal Bacteroides fragilis on host metabolism in high-fat diet-fed mice. Research results indicated that adding a specific bacterial strain to the complex intestinal microecology can worsen metabolic conditions. This effect mainly affects the structural diversity of intestinal microorganisms, the increase in harmful bacteria in the gut, and the elevation of endotoxin levels, blood glucose, and lipid metabolism, thereby impacting the progression of non-alcoholic fatty liver disease (NAFLD). Understanding the principles that govern the establishment of microbial communities comprising multiple species is crucial for preventing or repairing dysfunctions in these communities, thereby enhancing host health and facilitating disease treatment. This study demonstrated that gut microbiota dysbiosis could contribute to metabolic dysfunction and provides new insights into how to promote gut microbiota in the prevention and therapy of NAFLD.

Nutritional Characteristics, Health Impact, and Applications of Kefir

A global epidemiological shift has been observed in recent decades, characterized by an increase in age-related disorders, notably non-communicable chronic diseases, such as type 2 diabetes mellitus, cardiovascular and neurodegenerative diseases, and cancer. An appreciable causal link between changes in the gut microbiota and the onset of these maladies has been recognized, offering an avenue for effective management. Kefir, a probiotic-enriched fermented food, has gained significance in this setting due to its promising resource for the development of functional or value-added food formulations and its ability to reshape gut microbial composition. This has led to increasing commercial interest worldwide as it presents a natural beverage replete with health-promoting microbes and several bioactive compounds. Given the substantial role of the gut microbiota in human health and the etiology of several diseases, we conducted a comprehensive synthesis covering a total of 33 investigations involving experimental animal models, aimed to elucidate the regulatory influence of bioactive compounds present in kefir on gut microbiota and their potential in promoting optimal health. This review underscores the outstanding nutritional properties of kefir as a central repository of bioactive compounds encompassing micronutrients and amino acids and delineates their regulatory effects at deficient, adequate, and supra-nutritional intakes on the gut microbiota and their broader physiological consequences. Furthermore, an investigation of putative mechanisms that govern the regulatory effects of kefir on the gut microbiota and its connections with various human diseases was discussed, along with potential applications in the food industry.

Serine Supports Epithelial and Immune Cell Function in Colitis

Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders of the gastrointestinal tract that are largely driven by immune cell activity; mucosal healing is critical for remission. Serine is a nonessential amino acid that supports epithelial and immune cell metabolism and proliferation; however, whether these roles affect IBD pathogenesis is not well understood. Here, we show that serine synthesis increases selectively in the epithelial cells of colons from patients with IBD and murine models of colitis. Inhibiting serine synthesis impairs colonic mucosal healing and increases susceptibility to acute injury in mice, effects associated with impaired epithelial cell proliferation. Dietary removal of serine similarly sensitizes mice to acute chemically induced colitis but ameliorates inflammation in chronic colitis models. The anti-inflammatory effect of exogenous serine depletion in chronic colitis is associated with mitochondrial dysfunction of macrophages, resulting in impaired nucleotide production and proliferation. Collectively, these results suggest that serine plays an important role in both epithelial and immune cell biology in the colon and that modulating its availability could affect IBD pathogenesis.

The antioxidant strain Lactiplantibacillus plantarum AS21 and Clostridium butyricum ameliorate DSS-induced colitis in mice by remodeling the assembly of intestinal microbiota and improving gut functions

Probiotics are known for their beneficial effects on improving intestinal function by alleviating the gut microbial diversity. However, the influences of antioxidant lactic acid bacteria (LAB) and anti-inflammatory Clostridium butyricum (CB) on ameliorating enteritis remain unclear. In this study, we investigated the effects of the antioxidant strain Lactiplantibacillus plantarum AS21 and CB alone, or in combination on intestinal microbiota, barrier function, oxidative stress and inflammation in mice with DSS-induced colitis. All probiotic treatments relieved the pathological development of colitis by improving the integrity of the intestinal mucosal barrier and the length of the colon. The probiotics also suppressed inflammation and oxidative stress by improving gut short-chain fatty acids and inhibiting the p38-MAPK/NF-κB pathway in colon tissues. According to the meta-network analysis, three distinct modules containing sensitive OTUs of the gut bacterial community specific to the control, DSS and DSS + probiotics groups were observed, and unlike the other two modules, Lachnospiraceae and Clostridia dominated the sensitive OTUs in the DSS + probiotics group. In addition, administration of the present probiotics particularly increased antioxidant and anti-inflammatory microbes Muribaculaceae, Bifidobacterium, Prevotellaceae and Alloprevotella. Furthermore, combined probiotic strain treatment showed a more stable anti-colitis effect than a single probiotic strain. Collectively, the present probiotics exhibited protective effects against colitis by suppressing the inflammation and oxidative damage in the colon, improving the gut microbiota and their functions, and consequently preventing the gut leak. The results indicate that the combination of the antioxidant properties of LAB and the anti-inflammatory properties of CB as nutritional intervention and adjuvant therapy could be an effective strategy to prevent and alleviate colitis.

Protective Effect of the Polyphenol Ligustroside on Colitis Induced with Dextran Sulfate Sodium in Mice

Dietary polyphenols are reported to alleviate colitis by interacting with gut microbiota which plays an important role in maintaining the integrity of the intestinal barrier. As a type of dietary polyphenol, whether ligustroside (Lig) could alleviate colitis has not been explored yet. Here, we aimed to determine if supplementation of ligustroside could improve colitis. We explored the influence of ligustroside intake with different dosages on colitis induced with dextran sulfate sodium (DSS). Compared to the DSS group, supplementation of ligustroside could reduce body weight (BW) loss, decrease disease activity indices (DAI), and relieve colon damage in colitis mice. Furthermore, ligustroside intake with 2 mg/kg could decrease proinflammatory cytokine concentrations in serum and increase immunoglobulin content and antioxidant enzymes in colon tissue. In addition, supplementation of ligustroside (2 mg/kg) could reduce mucus secretion and prevent cell apoptosis. Also, changes were revealed in the bacterial community composition, microbiota functional profiles, and intestinal metabolite composition following ligustroside supplementation with 2 mg/kg using 16S rRNA sequencing and non-targeted lipidomics analysis. In conclusion, the results showed that ligustroside was very effective in preventing colitis through reduction in inflammation and the enhancement of the intestinal barrier. Furthermore, supplementation with ligustroside altered the gut microbiota and lipid composition of colitis mice.

Methyl cinnamate protects against dextran sulfate sodium-induced colitis in mice by inhibiting the MAPK signaling pathway

Effective and non-toxic therapeutic agents are lacking for the prevention and treatment of colitis. Previous studies found that methyl cinnamate (MC), extracted from galangal ( Alpinia officinarum Hance), has anti-inflammatory properties. However, whether MC is effective as anti-colitis therapy remains unknown. In this study, we investigate the therapeutic effects of MC on dextran sulfate sodium (DSS)-induced colitis in mice and further explore its potential mechanism of action. MC treatment relieves symptoms associated with DSS-induced colitis, including the recovery of DSS-induced weight loss, decreases the disease activity index score, and increases the colon length without toxic side effects. MC treatment protects the integrity of the intestinal barrier in mice with DSS-induced colitis and inhibits the overexpression of pro-inflammatory cytokines in vivo and in vitro. Moreover, the MAPK signaling pathway is found to be closely related to the treatment with MC of colitis. Western blot analysis show that phosphorylation of the p38 protein in colon tissues treated with MC is markedly reduced and phosphorylation levels of the p38, JNK and ERK proteins are significantly decreased in RAW 264.7 cells treated with MC, indicating that the mechanism of MC in treating DSS-induced colitis could be achieved by inhibiting the MAPK signaling pathway. Furthermore, 16S RNA sequencing analysis show that MC can improve intestinal microbial dysbiosis in mice with DSS-induced colitis. Altogether, these findings suggest that MC may be a novel therapeutic candidate with anti-colitis efficacy. Furthermore, MC treatment relieves the symptoms of colitis by inhibiting the MAPK signaling pathway and improving the intestinal microbiota.

Konjac glucomannan-assisted curcumin alleviated dextran sulfate sodium-induced mice colitis via regulating immune response and maintaining intestinal barrier integrity

Curcumin has been proven to be an effective strategy for reducing inflammatory responses. However, low bioavailability and instability at the physiological pH have limited its anti-inflammatory activity in ulcerative colitis patients. In the present study, a complex of curcumin and konjac glucomannan (KGM) effectively inhibited intestinal inflammation and this effect was associated with KGM degradation degrees. Results demonstrated that treatment with the complex markedly mitigated colitis symptoms and decreased inflammatory cytokines levels, especially in the complex treatment groups with K110 (KGM treated in 110 °C) and konjac oligosaccharides (KOSs). Furthermore, increasing the KOS content in KOC (the complex of curcumin and KOS) promoted the gene expressions of the intestinal barrier and inhibited the gene expressions of inflammatory cytokines, as well as improved gut microbiota dysregulation. Overall, our studies suggest that the complex of curcumin and KGM exerts effective anti-inflammatory effects by regulating the intestinal immune response and modulating microbiota diversity and composition.

Integrated 'omics analysis for the gut microbiota response to moxibustion in a rat model of chronic fatigue syndrome

OBJECTIVE

To observe the efficacy of moxibustion in the treatment of chronic fatigue syndrome (CFS) and explore the effects on gut microbiota and metabolic profiles.

METHODS

Forty-eight male Sprague-Dawley rats were randomly assigned to control group (Con), CFS model group (Mod, established by multiple chronic stress for 35 d), MoxA group (CFS model with moxibustion Shenque (CV8) and Guanyuan (CV4), 10 min/d, 28 d) and MoxB group (CFS model with moxibustion Zusanli (ST36), 10 min/d, 28 d). Open-field test (OFT) and Morris-water-maze test (MWMT) were determined for assessment the CFS model and the therapeutic effects of moxibustion.16S rRNA gene sequencing analysis based gut microbiota integrated untargeted liquid chromatograph-mass spectrometer (LC-MS) based fecal metabolomics were executed, as well as Spearman correlation analysis, was utilized to uncover the functional relevance between the potential metabolites and gut microbiota.

RESULTS

The results of our behavioral tests showed that moxibustion improved the performance of CFS rats in the OFT and the MWMT. Microbiome profiling analysis revealed that the gut microbiomes of CFS rats were less diverse with altered composition, including increases in pro-inflammatory species (such as Proteobacteria) and decreases in anti-inflammatory species (such as Bacteroides, Lactobacillus, Ruminococcus, and Prevotella). Moxibustion partially normalized these changes in the gut microbiota. Furthermore, CFS was associated with metabolic disorders, which were effectively ameliorated by moxibustion. This was demonstrated by the normalization of 33 microbiota-related metabolites, including mannose (P = 0.001), aspartic acid (P = 0.009), alanine (P = 0.007), serine (P = 0.000), threonine (P = 0.027), methionine (P = 0.023), 5-hydroxytryptamine (P = 0.008), alpha-linolenic acid (P = 0.003), eicosapentaenoic acid (P = 0.006), hypoxanthine (P = 0.000), vitamin B6 (P = 0.000), cholic acid (P = 0.013), and taurocholate (P = 0.002). Correlation analysis showed a significant association between the perturbed fecal microbiota and metabolite levels, with a notable negative relationship between LCA and Bacteroides.

CONCLUSIONS

In this study, we demonstrated that moxibustion has an antifatigue-like effect. The results from the 16S rRNA gene sequencing and metabolomics analysis suggest that the therapeutic effects of moxibustion on CFS are related to the regulation of gut microorganisms and their metabolites. The increase in Bacteroides and decrease in LCA may be key targets for the moxibustion treatment of CFS.

Saccharomyces boulardii protects against murine experimental colitis by reshaping the gut microbiome and its metabolic profile

Introduction

Saccharomyces boulardii (S. boulardii) has shown clinical beneficial effect in inflammatory bowel diseases recently. However, the underlying mechanisms remain incompletely understood. The aim of present study was to tested whether S. boulardii targets gut microbiota to protect against the development of experimental colitis in mice.

Methods

Female C57BL/6 mice were gavaged with S. boulardii for 3 weeks before being challenged with dextran sulphate sodium to induce ulcerative colitis. Bodyweight, diarrhea severity, intestinal permeability, colonic histopathology, colonic inflammatory status, and epithelial cell death of mice were examined. The fecal microbiota and its metabolomic profiles were detected by 16S rDNA sequencing and UPLC-MS, respectively.

Results and Discussion

Supplementation with S. boulardii significantly prevented weight loss and colon shortening, lowered colonic inflammation, ameliorated epithelial injury, and enhanced the intestinal barrier integrity in colitis mice. By inhibiting the abundance of pathogenic bacteria and increasing the probiotics abundance, S. boulardii improved the microbial diversity and restored the microbiota dysbiosis. Moreover, it also modulated microbial metabolome and altered the relative contents of metabolites involving amino acids, lipids, energy and vitamin metabolisms. These yeast-driven shifts in gut flora and metabolites are were associated with each other and with the inflammation profile in colitis. Collectively, S. boulardii exerts protective effects on colitis in mice by reshaping gut microbiome and its metabolic profile, indicating it as a promising therapeutic avenue.

Whole intestinal microbiota transplantation is more effective than fecal microbiota transplantation in reducing the susceptibility of DSS-induced germ-free mice colitis

Fecal microbiota transplantation (FMT) is an emerging and effective therapy for the treatment of inflammatory bowel disease (IBD). Previous studies have reported that compared with FMT, whole intestinal microbiota transplantation (WIMT) can more precisely replicate the community structure and reduce the inflammatory response of the host. However, it remains unclear whether WIMT is more effective in alleviating IBD. To examine the efficacy of WIMT and FMT in the intervention of IBD, GF (Germ-free) BALB/c mice were pre-colonized with whole intestinal microbiota or fecal microbiota before being treated with dextran sodium sulfate (DSS). As expected, the symptoms of colitis were alleviated by both WIMT and FMT, as demonstrated by the prevention of body weight loss and decreased the Disease activity index and histological scores in mice. However, WIMT's anti-inflammatory effect was superior to that of FMT. In addition, the inflammatory markers myeloperoxidase (MPO) and eosinophil peroxidase were dramatically downregulated by WIMT and FMT. Furthermore, the use of two different types of donors facilitated the regulation of cytokine homeostasis in colitis mice; the level of the pro-inflammatory cytokine IL-1β in the WIMT group was significantly lower than that in the FMT group, while the level of the anti-inflammatory factor IL-10 was significantly higher than that in the FMT group. Both groups showed enhanced expression of occludin to protect the intestinal barrier in comparison with the DSS group, and the WIMT group demonstrated considerably increased levels of ZO-1. The sequencing results showed that the WIMT group was highly enriched in Bifidobacterium, whereas the FMT group was significantly enriched in Lactobacillus and Ochrobactrum. Correlation analysis revealed that Bifidobacterium was negatively correlated with TNF-α, whereas Ochrobactrum was positively correlated with MPO and negatively correlated with IL-10, which might be related to different efficacies. Functional prediction using PICRUSt2 revealed that the FMT group was considerably enriched in the L-arginine biosynthesis I and L-arginine biosynthesis IV pathway, whereas the WIMT group was enriched in the L-lysine fermentation to acetate and butanoate pathway. In conclusion, the symptoms of colitis were subsided to varying degrees by the two different types of donors, with the WIMT group being more effective than the FMT group. This study provides new information on clinical interventions for IBD.

Bovine milk-derived extracellular vesicles prevent gut inflammation by regulating lipid and amino acid metabolism

Inflammatory bowel disease (IBD) is a global health problem in which metabolite alteration plays an important pathogenic role. Bovine milk-derived extracellular vesicles (mEVs) have been shown to regulate nutrient metabolism in healthy animal models. This study investigated the effect of oral mEVs on metabolite changes in DSS-induced murine colitis. We performed metabolomic profiling on plasma samples and measured the concentrations of lipids and amino acids in both fecal samples and colonic tissues. Plasma metabolome analysis found that mEVs significantly upregulated 148 metabolite levels and downregulated 44 metabolite concentrations (VIP > 1, and p < 0.05). In the fecal samples, mEVs significantly increased the contents of acetate and butyrate and decreased the levels of tridecanoic acid (C13:0), methyl cis-10-pentadecenoate (C15:1) and cis-11-eicosenoic acid (C20:1). Moreover, the concentrations of eicosadienoic acid (C20:2), eicosapentaenoic acid (C20:5), and docosahexaenoic acid (C22:6) were decreased in colonic tissues with mEV supplementation. In addition, compared with the DSS group, mEVs significantly increased the content of L-arginine, decreased the level of L-valine in the fecal samples, and also decreased the levels of L-serine and L-glutamate in the colonic tissues. Collectively, our findings demonstrated that mEVs could recover the metabolic abnormalities caused by inflammation and provided novel insights into mEVs as a potential modulator for metabolites to prevent and treat IBD.

Administration of selenomethionine in combination with serine benefits diabetes via gut microbiota

Either selenium or serine could modulate glucose homeostasis, however, whether there are synergistic effects of selenium with serine on diabetes remains to be unknown. In the present study, eight male db/m mice were used as a control, and 24 male diabetic db/db mice were either orally gavaged with PBS, or with selenomethionine alone, or with both selenomethionine and serine, to investigate the effects of selenomethionine and serine on body weight and glucose level. Furthermore, intestinal microbiota composition was analyzed and fecal microbiota transplantation (FMT) was performed to explore whether microbes mediate the beneficial effects of selenomethionine and serine. The results showed that administration of selenomethionine decreased body weight, adipose tissue weight and serum glucose level in db/db diabetic mice. Importantly, administration of selenomethionine in combination with serine exerted better effects than selenomethionine alone did. Furthermore, a combined administration of selenomethionine and serine restored the microbial composition in diabetic mice. Corynebacterium glutamicum, Bifidobacterium pseudolongum, and Aerococcus urinaeequi were significantly decreased, whereas Lactobacillus murinus was increased in mice in the selenomethionine group and selenomethionine in combination with serine group, when compared with those in the db/db group. FMT decreased body weight and glucose level in db/db mice, further indicating that microbes play critical roles in the beneficial effects of selenomethionine and serine. Thus, we concluded that administration of selenomethionine in combination with serine benefits diabetes via gut microbes. Our results suggested that the synergic application of selenomethionine and serine could be potentially used for the treatment of diabetes.

L-serine improves lipid profile, performance, carcass weight and intestinal parameters in feed restricted broiler chickens during the hot-dry season

The study evaluated effects of L-serine on lipid profile, performance, carcass weight and small intestinal parameters in heat-stressed broiler chickens subjected to feed restriction. Broiler chickens were divided into four groups, comprising 30 each. Group 1, feed restriction (FR); Group 2, feed restriction + L-serine (200 mg/kg) (FR + L-serine); Group 3, ad libitum (AL); Group 4, ad libitum + L-serine (200 mg/kg) (AL + L-serine). L-serine was administered orally from days 1 to 14, and feed restriction was performed on days 7-14. Serum harvested from blood samples on days 21, 28 and 35 was evaluated for lipid profile. Feed and water intake, live weight gain, organ and carcass weight were measured. At 35 days old, broiler chickens (n = 7) per group were sacrificed to evaluate small intestinal morphology. Temperature-humidity index in the pen (30.88 ± 0.81) was above thermoneutral zone, indicating that chickens were subjected to heat stress. Concentrations of low-density lipoprotein, total cholesterol and total triglycerides were lower (p < 0.05), while higher concentration of high-density lipoprotein was recorded in L-serine groups than in the controls. Feed intake and live weight gain on day 35 in L-serine groups were higher (p < 0.05) than in controls. In L-serine groups, liver, spleen, pancreas and heart weight were higher, but abdominal fat was lower than in FR and AL groups. Villus height:crypt height ratio and area of villus surface were highest in L-serine groups than any other group. In conclusion, L-serine decreased low-density lipoprotein, increased feed intake, live weight, organ and carcass weight, villus height:crypt height ratio and villus surface area.

Association of human gut microbiota composition and metabolic functions with Ficus hirta Vahl dietary supplementation

Ficus hirta Vahl (FHV), a traditional herbal ingredient of the tonic diet, receives increasing popularity in southern China. However, it is largely unknown that how a FHV diet (FHVD) affects the human gut microbiome. In this exploratory study, a total of 43 healthy individuals were randomized into the FHVD (n = 25) and Control (n = 18) groups to receive diet intervention for 8 weeks. 16S rRNA gene sequencing, metagenomic sequencing and metabolic profile of participants were measured to assess the association between FHV diet and gut microbiome. A preservation effect of Faecalibacterium and enrichment of Dialister, Veillonella, Clostridium, and Lachnospiraceae were found during the FHVD. Accordingly, the pathway of amino acid synthesis, citrate cycle, coenzyme synthesis, and partial B vitamin synthesis were found to be more abundant in the FHVD. In addition, serine, glutamine, gamma-aminobutyric acid, tryptamine, and short-chain fatty acids (SCFAs) were higher after the FHVD. The conjoint analysis of FHV components and in-vitro fermentation confirmed that the improved SCFAs concentration was collectively contributed by the increasing abundance of key enzyme genes and available substrates. In conclusion, the muti-omics analysis showed that the FHVD optimized the structure of the gut microbial community and its metabolic profile, leading to a healthy tendency, with a small cluster of bacteria driving the variation rather than a single taxon.

A phage cocktail combined with the enteric probiotic Lactobacillus reuteri ameliorated mouse colitis caused by S. typhimurium

Salmonella enterica serovar Typhimurium (S. typhimurium) is one of the most important foodborne pathogens that causes colitis in humans. In this study, we compared the effects of a therapeutic treatment using a phage cocktail (Pc) in combination or not with Lactobacillus reuteri (L. reuteri) in an S. typhimurium-induced colitis murine model. An oral administration of 4 × 10⁸ CFU per mouse of S. typhimurium resulted in intestinal barrier disruption and severe inflammatory symptoms. S. typhimurium in the colon of the mice treated with the Pc and L. reuteri (PcLR) combination were completely removed compared to those in the single Pc or single L. reuteri treatment groups. Furthermore, compared with the infected group, the intestinal barrier and colonic pathological damage were significantly improved in the PcLR-treated group. Additionally, the short-chain fatty acid (SCFA) levels in the feces of the mice in the PcLR treatment group were significantly increased compared to those in the feces of the mice in the infected group. In addition, the combination of Pc with acetate and reuterin released by L. reuteri (PcReAc) can also achieve the same effect as PcLR treatment. Thus, these results indicated that the acetate and reuterin released by L. reuteri play an important role in the treatment. The extraordinary therapeutic effects of PcLR and PcReAc depend on the specific bactericidal activity of Pc and the broad-spectrum bactericidal activity and immunomodulation of L. reuteri (or acetate and reuterin) in the host. This study provides a new concept for the treatment of inflammatory diseases caused by intestinal pathogens.

The Combination of Phages and Faecal Microbiota Transplantation Can Effectively Treat Mouse Colitis Caused by Salmonella enterica Serovar Typhimurium

Salmonella enterica serovar Typhimurium (S. Typhimurium) is one of the common causes of human colitis. In the present study, two lytic phages vB_SenS-EnJE1 and vB_SenS-EnJE6 were isolated and the therapeutic effect of the combination of phages and faecal microbiota transplantation (FMT) on S. Typhimurium-induced mouse colitis was investigated. The characteristics and genome analysis indicated that they are suitable phages for phage therapy. Results showed that vB_SenS-EnJE1 lysis 41/54 Salmonella strains of serotype O4, and vB_SenS-EnJE6 lysis 46/54 Salmonella strains of serotypes O4 and O9. Severe inflammatory symptoms and disruption of the intestinal barrier were observed in S. Typhimurium -induced colitis. Interestingly, compared with a single phage cocktail (Pc) or single FMT, the combination of Pc and FMT (PcFMT) completely removed S. Typhimurium after 72 h of treatment, and significantly improved pathological damage and restored the intestinal barrier. Furthermore, PcFMT effectively restored the intestinal microbial diversity, especially for Firmicutes/Bacteroidetes [predominantly bacterial phyla responsible for the production of short-chain fatty acids (SCFA)]. Additionally, we found that PcFMT treatment significantly increased the levels of SCFA. All these data indicated that the combination of phages and FMT possesses excellent therapeutic effects on S. Typhimurium -induced intestinal microbiota disorder diseases. Pc and FMT played roles in “eliminating pathogens” and “strengthening vital qi,” respectively. This study provides a new idea for the treatment of intestinal microbiota disorder diseases caused by specific bacterial infections.

Intestinal accumulation of microbiota-produced succinate caused by loss of microRNAs leads to diarrhea in weanling piglets

Diarrheal disease is a common health problem with complex causality. Although diarrhea is accompanied by disturbances in microbial diversity, how gut microbes are involved in the occurrence of diarrhea remains largely unknown. Here, using a pig model of post-weaning stress-induced diarrhea, we aim to elucidate and enrich the mechanistic basis of diarrhea. We found significant alterations in fecal microbiome, their metabolites, and microRNAs levels in piglets with diarrhea. Specifically, loss of ssc-miRNA-425-5p and ssc-miRNA-423-3p, which inhibit the gene expression of fumarate reductase (frd) in Prevotella genus, caused succinate accumulation in piglets, which resulted in diarrhea. Single-cell RNA sequencing indicated impaired epithelial function and increased immune response in the colon of piglet with diarrhea. Notably, the accumulated succinate increased colonic fluid secretion by regulating transepithelial Cl-secretion in the epithelial cells. Meanwhile, succinate promoted colonic inflammatory responses by activating MyD88-dependent TLR4 signaling in the macrophages. Overall, our findings expand the mechanistic basis of diarrhea and suggest that colonic accumulation of microbiota-produced succinate caused by loss of miRNAs leads to diarrhea in weanling piglets.

Gancao Xiexin Decoction Ameliorates Ulcerative Colitis in Mice via Modulating Gut Microbiota and Metabolites

Purpose

Ulcerative colitis (UC) is a chronic inflammatory bowel disease that starts with mucosal inflammation of the rectum and extends proximally in the colon in a continuous manner over a variable distance. Although it is more common in North America and Western Europe, its incidence is also increasing in Asia. Despite the introduction of several different classes of medications, the treatment options for UC may be insufficiently effective and burdened with significant side effects. In the present study, the therapeutic effects of Gancao Xiexin decoction (GCXX) were investigated on mice with dextran sulfate sodium (DSS)-induced colitis with exploration of the underlying mechanisms.

Methods

Colitis was induced in C57BL/6 mice by administering 3% DSS in drinking water for 7 days. GCXX and (or) the standard of care anti-inflammatory drug, mesalazine (5-aminosalicylic acid) were then administered for 7 days. The gut microbiota was characterized by 16S rDNA high-throughput gene sequencing and gut metabolites were detected by untargeted metabolomics. Germ-free mice were subsequently used to determine whether GCXX ameliorated UC principally through modulation of the gut microbiota.

Results

GCXX treatment was demonstrated to significantly reduce disease activity index (DAI) scores, prevent colonic shortening, ameliorate colonic tissue damage and reduce the levels of pro-inflammatory cytokines. Furthermore, analysis of the gut microbiota showed that GCXX-treated mice had higher relative quantity of Dubosiella (P<0.05) and lower relative quantity of Escherichia-Shigella (P<0.05). Metabolomics analysis indicated that GCXX could reduce the level of linoleic acid (P<0.05) and regulate its metabolism pathway. Moreover, in germ-free mice, GCXX failed to increase body weight, reduce DAI scores, or alleviate either colonic shortening or colonic damage.

Conclusion

The present study demonstrated that GCXX ameliorated DSS-induced colitis principally through modulating the gut microbiota and metabolites. This information should be integrated into the overall mechanisms of GCXX treatment of UC.

L-Serine Supplementation Blunts Fasting-Induced Weight Regain by Increasing Brown Fat Thermogenesis

Weight regain after fasting, often exceeding the pre-fasting weight, is a common phenomenon and big problem for the treatment of obesity. Thus, novel interventions maintaining reduced body weight are critically important to prevent metabolic disease. Here we investigate the metabolic effects of dietary L-serine supplementation, known to modulate various organ functions. C57BL/6N-Rj male mice were supplemented with or without 1% L-serine in their drinking water and fed with a chow or high-fat diet. Mice were fed either ad libitum or subjected to repeated overnight fasting. Body weight, body composition, glucose tolerance and energy metabolism were assessed. This was combined with a detailed analysis of the liver and adipose tissues, including the use of primary brown adipocytes to study mitochondrial respiration and protein expression. We find that L-serine supplementation has little impact on systemic metabolism in ad libitum-fed mice. Conversely, L-serine supplementation blunted fasting-induced body weight regain, especially in diet-induced obese mice. This reduction in body weight regain is likely due to the increased energy expenditure, based on elevated brown adipose tissue activity. Thus, L-serine supplementation during and after weight-loss could reduce weight regain and thereby help tackle one of the major problems of current obesity therapies.

In vivo and in silico studies on the mechanisms of egg white peptides in relieving acute colitis symptoms

Active peptides, as an alternative nutrition supplement, have been confirmed to have beneficial efficacy against acute colitis. Herein, egg white peptides (EWPs) were used as a nutritional supplement to relieve dextran sulfate sodium-induced acute colitis symptoms. The potential multi-component synergetic pharmacological intervention mechanism of EWPs was investigated on the basis of in silico pharmacology, bioinformatics analysis, and molecular docking. In vitro experiments demonstrated that the migration rate of HSF cells was enhanced 5.30-fold upon treatment with EWPs relative to the control group. After administration with EWPs, colitis symptoms were alleviated in a dose-dependent manner and the serum amino acid content was significantly enhanced, especially for Ala, Leu, Ser, Thr, and Met. Four peptides identified from EWPs showed a total of 52 acute colitis-related potential targets (Fit score >3.8) with network pharmacology analysis, and the targets participated in 31 signaling pathways (p < 0.001). Among these pathways, PI3K-Akt, VEGF, Ras, TNF, and MAPK signaling pathways may exert essential anti-inflammatory effects and accelerate repairing intestinal mucosa. Molecular docking showed that the majority binding energy of peptides-targets was between -10.35 kcal mol^-1 and -18.72 kcal mol^-1, and peptides mainly interacted with the core targets (Btk, Gstm1, and Rac1) by hydrogen-bonding interactions. The current study confirmed that EWPs as supplementary nutrition can alleviate acute colitis.

Exogenous and Endogenous Serine Deficiency Exacerbates Hepatic Lipid Accumulation

Serine is involved in the regulation of hepatic lipid metabolism. However, whether exogenous or endogenous serine deficiency affects lipid accumulation in the liver and related mechanisms is unclear. Here, we investigated the effects of serine deficiency on hepatic fat accumulation in mice fed a serine-deficient diet or in mice supplemented with the D-3-phosphoglycerate dehydrogenase (PHGDH) inhibitor NCT-503. Both treatments produced an increase in body weight and liver weight and higher triglyceride content in the liver. Both treatments also exacerbated hepatic inflammatory responses and oxidative stress. Importantly, NCT-503 supplementation significantly inhibited PHGDH activity and decreased the serine content in the liver. Dietary serine deficiency significantly affected the colonic microbiota, characterized by a decreased ratio of Firmicutes/Bacteroidetes and decreased proportion of Bifidobacterium. Dietary serine deficiency additionally resulted in significantly decreased colonic and serum acetate and butyrate levels. The collective results indicate that NCT-503 supplementation may contribute to overaccumulation of hepatic lipid, by causing hepatic serine deficiency, while dietary serine deficiency may produce similar outcomes by affecting the gut-microbiota-liver axis.

Effects of Essential Oils and Selected Compounds from Lamiaceae Family as Adjutants on the Treatment of Subjects with Periodontitis and Cardiovascular Risk

Essential oils from different plant species were found to contain different compounds exhibiting anti-inflammatory effects with the potential to be a valid alternative to conventional chemotherapy that is limited in long-term use due to its serious side effects. Generally, the first mechanism by which an organism counteracts injurious stimuli is inflammation, which is considered a part of the innate immune system. Periodontitis is an infectious and inflammatory disease caused by a dysbiosis in the subgingival microbiome that triggers an exacerbated immune response of the host. The immune–inflammatory component leads to the destruction of gingival and alveolar bone tissue. The main anti-inflammation strategies negatively modulate the inflammatory pathways and the involvement of inflammatory mediators by interfering with the gene’s expression or on the activity of some enzymes and so affecting the release of proinflammatory cytokines. These effects are a possible target from an effective and safe approach, suing plant-derived anti-inflammatory agents. The aim of the present review is to summarize the current evidence about the effects of essentials oils from derived from plants of the Lamiaceae family as complementary agents for the treatment of subjects with periodontitis and their possible effect on the cardiovascular risk of these patients.

Effect of dietary serine supplementation on performance, egg quality, serum indices, and ileal mucosal immunity in laying hens fed a low crude protein diet

This study was designed to evaluate the effect of dietary Ser on performance, egg quality, serum indices, and ileal mucosal immunity in laying hens fed low crude protein (LCP), essential amino acids (EAA) balanced diets. A total of 480 Hy-Line Brown layers at 24 wk of age were randomly assigned into 5 dietary treatments with 8 replicates of 12 birds each. Treatments included a control diet (16.49% CP), and 4 LCP, EAA balanced diets (14.05% CP) supplemented with 0, 0.114%, 0.306%, 0.498% L-Ser, respectively. Dietary Ser supplementation linearly increased hen-day egg production (HDEP; P < 0.05) and decreased feed-to-egg ratio (P < 0.05) among LCP groups from wk 6 to 10, and the optimal HDEP of layers occurred at Ser level of 0.498%. At the end of wk 10, birds in the control had higher albumen height and thick white proportion than those fed the LCP diet without Ser addition (P < 0.05), and presented a lower yolk color score than all LCP groups (P < 0.05). Among LCP groups, serum total protein and globulin contents were significantly increased by dietary Ser addition at the levels of 0.306% and 0.498% (P < 0.05), and had a linear response to the supplemental Ser levels (P < 0.05). Furthermore, dietary 0.498% Ser supplementation significantly increased serum immunoglobulin G and immunoglobulin M contents (P < 0.05) and up-regulated the expression of mucin 2, secretory immunoglobulin A, and relevant glycosyltransferases of O-glycosylation in ileal mucosa (P < 0.05). The increased expression of proinflammatory cytokines IFN-γ and IL-1β induced by LCP diets (P < 0.05) was reversed following 0.498% Ser addition (P < 0.05). Collectively, dietary CP reduction by 2.44% could maintain the productive performance of layers when it was fortified with certain EAA, though poor albumen quality, and ileal inflammation were occurred. The addition of Ser to LCP diets improved performance probably through enhancing humoral and ileal mucosal immunity and attenuating the ileal inflammation of layers.

Dietary Supplementation with Glycine Enhances Intestinal Mucosal Integrity and Ameliorates Inflammation in C57BL/6J Mice with High-Fat Diet-Induced Obesity

BACKGROUND

Obesity, a major public health problem worldwide, is associated with dysfunction of the intestinal barrier. Glycine (Gly) has been reported to enhance the expression of tight-junction proteins in porcine enterocytes. It is unknown whether Gly can improve intestinal barrier integrity in obese mice.

OBJECTIVES

This study tested the hypothesis that Gly enhances the intestinal epithelial barrier by regulating endoplasmic reticulum (ER) stress-related signaling and mitigating inflammation in high-fat diet (HFD)-induced obese mice.

METHODS

Five-week-old male C57BL/6J mice were fed a normal-fat diet (ND; fat = 10% energy) or an HFD (fat = 60% energy) and received drinking water supplemented with 2% Gly or 2.37% l-alanine (Ala; isonitrogenous control) daily for 12 wk. Body weight gain and tissue weights, glucose tolerance and the activation of immune cells, as well as the abundances of tight-junction proteins, ER stress proteins, and apoptosis-related proteins in the jejunum and colon were determined. In addition, the body weights of naïve ND and HFD groups (nND and nHFD, respectively) were also recorded for comparison. Differences were analyzed statistically by ANOVA followed by the Duncan multiple-comparison test using SAS software.

RESULTS

Compared with ND-Ala, HFD-feeding resulted in enhanced macrophage (CD11b+ and F4/80+) infiltration and immune cell activation by 1.9- to 5.4-fold (P < 0.05), as well as the upregulation of ER stress sensor proteins (including phospho-inositol-requiring enzyme 1α and binding immunoglobulin protein) by 2.5- to 4.5-fold, the induction of apoptotic proteins by 1.5- to 3.2-fold, and decreased abundances of tight-junction proteins by 35%-65% (P < 0.05) in the intestine. These HFD-induced abnormalities were significantly ameliorated by Gly supplementation in the HFD-Gly group (P < 0.05). Importantly, Gly supplementation also significantly enhanced glucose tolerance (P < 0.05) by 1.5-fold without affecting the fat accumulation of HFD-induced obese mice.

CONCLUSIONS

Gly supplementation enhanced the intestinal barrier and ameliorated inflammation and insulin resistance in HFD-fed mice. These effects of Gly were associated with reduced ER stress-related apoptosis in the intestine of obese mice.

Dietary Bioactive Peptide Alanyl-Glutamine Attenuates Dextran Sodium Sulfate-Induced Colitis by Modulating Gut Microbiota

Inflammatory bowel disease (IBD) is a chronic intestinal disorder threatening human health. Di-peptide alanyl-glutamine (Ala-Gln) has various beneficial effects on gut health. However, its role and functional mechanism in treating IBD are still not clear. Therefore, the protective effects of Ala-Gln and glutamine (Gln) on dextran sulfate sodium- (DSS-) induced colitic mice were investigated in this study. The results showed that oral supplementation of Ala-Gln or Gln significantly attenuated the colitis symptoms in mice, including body weight loss, colon length, disease activity index, histological scores, and tissue apoptosis. The concentrations of interleukin- (IL-) 1β, IL-6, tumor necrosis factor-α, and myeloperoxidase were significantly decreased, while the concentrations of immunoglobulins (IgA, IgG, and IgM) and superoxide dismutase were significantly increased by Ala-Gln or Gln supplementation. The expression of occludin and peptide transporter 1 (PepT1) was significantly increased by Ala-Gln or Gln. Interestingly, Ala-Gln had better beneficial effects than Gln in alleviating colitis. In addition, 16S rDNA sequencing showed that the DSS-induced shifts of the microbiome (community diversity, evenness, richness, and composition) in the mouse colon were restored by Gln and Ala-Gln, including Lactobacillus, Bacteroides_acidifaciens, Bacteroidales, Firmicutes, Clostridia, Helicobacter, and Bacteroides. Correspondingly, the functions of the microflora metabolism pathways were also rescued by Ala-Gln, including fatty acid metabolism, membrane transporters, infectious diseases, and immune system. In conclusion, the results revealed that Ala-Gln can prevent colitis through PepT1, enhancing the intestinal barrier and modulating gut microbiota and microflora metabolites.

Diet-Microbiota Interactions in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract. Although the precise etiology of IBD is largely unknown, it is widely thought that diet contributes to the development of IBD. Diet shapes the composition of the gut microbiota, which plays critical roles in intestinal homeostasis. In contrast, intestinal inflammation induces gut dysbiosis and may affect the use of dietary nutrients by host cells and the gut microbiota. The interaction of diet and the gut microbiota is perturbed in patients with IBD. Herein, we review the current knowledge of diet and gut microbiota interaction in intestinal homeostasis. We also discuss alterations of diet and gut microbiota interaction that influence the outcome and the nutritional treatment of IBD. Understanding the complex relationships between diet and the gut microbiota provides crucial insight into the pathogenesis of IBD and advances the development of new therapeutic approaches.

Dietary Taxifolin Protects Against Dextran Sulfate Sodium-Induced Colitis via NF-κB Signaling, Enhancing Intestinal Barrier and Modulating Gut Microbiota

Taxifolin is a natural antioxidant polyphenol with various bioactivities and has many beneficial effects on human gut health. However, little is known of its function on colitis. In this study, the protective effects of taxifolin on colitis symptoms, inflammation, signaling pathways, and colon microbiota were investigated using dextran sulfate sodium (DSS)-induced colitis mice. Intriguingly, pre-administration of taxifolin alleviated the colitis symptoms and histological changes of the DSS-challenged mice. Supplementation of taxifolin significantly inhibited the secretions of tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 and significantly increased the secretions of IL-10, secretory immunoglobulin A, superoxide dismutase, and immunoglobulins (IgA, IgG, and IgM) in DSS-induced colitis mice. In addition, the activation of nuclear factor kappa B (NF-κB; p65 and IκBα) signaling was significantly suppressed by taxifolin supplementation. The expression of tight junction proteins (claudin-1 and occludin) was significantly increased by taxifolin. Moreover, 16S rDNA sequencing revealed that the DSS-induced changes of colon microbiota composition and microbial functions (amino acid metabolism and MAPK signaling) were restored by taxifolin, including the decreases of the abundances of Bacteroides, Clostridium ramosum, Clostridium saccharogumia, Sphingobacterium multivorum, and the ratio of Bacteroidetes/Firmicutes, and the increases of the abundances of Desulfovibrio C21 c20 and Gemmiger formicilis at species level. In conclusion, these results revealed that dietary taxifolin has a great potential to prevent colitis by inhibiting the NF-κB signaling pathway, enhancing intestinal barrier, and modulating gut microbiota.

Anti-Inflammatory and Intestinal Microbiota Modulation Properties of Jinxiang Garlic (Allium sativum L.) Polysaccharides toward Dextran Sodium Sulfate-Induced Colitis

Garlic polysaccharides are great potential agents because of their anti-inflammation, antioxidation, and immunomodulation properties. However, few studies have reported their anti-inflammatory effects on improving the colon system and corresponding intestinal microbiota. Herein, a water-soluble garlic polysaccharide (WSGP) was extracted from Jinxiang garlic to evaluate its effects on ameliorating dextran sulfate sodium (DSS)-induced colitis in a mouse model. The results showed that (1) after administration of the WSGP (200 or 400 mg/kg/day), the feed intake, body weight, and colon length of colitic mice were increased, while the disease activity index and the histological score of colitic mice were decreased; (2) the WSGP reduced the colonic tissue damage and inhibited the expression of inflammatory factors (interleukin 6, interleukin 1 beta , and tumor necrosis factor alpha); and (3) the WSGP enhanced the production of short-chain fatty acids and improved the composition of intestinal microbiota. The key microorganisms, including Muribaculaceae, Lachnospiraceae, Lachnospiraceae_NK4A136_group, Mucispirillum, Helicobacter, Ruminococcus_1, and Ruminiclostridium_5, were identified to be associated with inflammatory bowel diseases. Taken together, this study proved that WSGP supplementation could alleviate DSS-induced colitis by improving mucosal barriers, blocking proinflammatory cytokines, and modulating gut microbiota.

Exclusive enteral nutrition mediates gut microbial and metabolic changes that are associated with remission in children with Crohn's disease

A nutritional intervention, exclusive enteral nutrition (EEN) can induce remission in patients with pediatric Crohn's disease (CD). We characterized changes in the fecal microbiota and metabolome to identify the mechanism of EEN. Feces of 43 children were collected prior, during and after EEN. Microbiota and metabolites were analyzed by 16S rRNA gene amplicon sequencing and NMR. Selected metabolites were evaluated in relevant model systems. Microbiota and metabolome of patients with CD and controls were different at all time points. Amino acids, primary bile salts, trimethylamine and cadaverine were elevated in patients with CD. Microbiota and metabolome differed between responders and non-responders prior to EEN. EEN decreased microbiota diversity and reduced amino acids, trimethylamine and cadaverine towards control levels. Patients with CD had reduced microbial metabolism of bile acids that partially normalized during EEN. Trimethylamine and cadaverine inhibited intestinal cell growth. TMA and cadaverine inhibited LPS-stimulated TNF-alpha and IL-6 secretion by primary human monocytes. A diet rich in free amino acids worsened inflammation in the DSS model of intestinal inflammation. Trimethylamine, cadaverine, bile salts and amino acids could play a role in the mechanism by which EEN induces remission. Prior to EEN, microbiota and metabolome are different between responders and non-responders.

Inulin supplementation ameliorates hyperuricemia and modulates gut microbiota in Uox-knockout mice

Purpose

Inulin is a type of fermentable dietary fiber, which is non-digestible, and can improve metabolic function by modulating intestinal microbiota. This study aimed to evaluate the role of inulin in hyperuricemia and microbial composition of the gut microbiota in a mouse model of hyperuricemia established through knockout of Uox (urate oxidase) gene.

Methods

KO (Uox-knockout) and WT (wild-type) mice were given inulin or saline by gavage for 7 weeks. The effect of inulin to combat hyperuricemia was determined by assessing the changes in serum UA (uric acid) levels, inflammatory parameters, epithelial barrier integrity, fecal microbiota alterations, and SCFA (short-chain fatty acid) concentrations in KO mice.

Results

Inulin supplementation can effectively alleviate hyperuricemia, increase the expressions of ABCG2 in intestine, and downregulate expression and activity of hepatic XOD (xanthine oxidase) in KO mice. It was revealed that the levels of inflammatory cytokines and the LPS (lipopolysaccharide) were remarkably higher in the KO group than those in the WT group, indicating systemic inflammation of hyperuricemic mice, but inulin treatment ameliorated inflammation in KO mice. Besides, inulin treatment repaired the intestinal epithelial barrier as evidenced by increased levels of intestinal TJ (tight junction) proteins [ZO-1 (zonula occludens-1) and occluding] in KO mice. Moreover, serum levels of uremic toxins, including IS (indoxyl sulfate) and PCS (p-cresol sulfate), were reduced in inulin-treated KO mice. Further investigation unveiled that inulin supplementation enhanced microbial diversity and raised the relative abundance of beneficial bacteria, involving SCFAs-producing bacteria (e.g., Akkermansia and Ruminococcus). Additionally, inulin treatment increased the production of gut microbiota-derived SCFAs (acetate, propionate and butyrate concentrations) in KO mice, which was positively correlated with the effectiveness of hyperuricemia relief.

Conclusions

Our findings showed that inulin may be a promising therapeutic candidate for the treatment of hyperuricemia. Moreover, alleviation of hyperuricemia by inulin supplementation was, at least, partially conciliated by modulation of gut microbiota and its metabolites.

Electronic supplementary material

The online version of this article (10.1007/s00394-020-02414-x) contains supplementary material, which is available to authorized users.

Serine administration as a novel prophylactic approach to reduce the severity of acute pancreatitis during diabetes in mice

AIMS/HYPOTHESIS

Compared with the general population, individuals with diabetes have a higher risk of developing severe acute pancreatitis, a highly debilitating and potentially lethal inflammation of the exocrine pancreas. In this study, we investigated whether 1-deoxysphingolipids, atypical lipids that increase in the circulation following the development of diabetes, exacerbate the severity of pancreatitis in a diabetic setting.

METHODS

We analysed whether administration of an L-serine-enriched diet to mouse models of diabetes, an established method for decreasing the synthesis of 1-deoxysphingolipids in vivo, reduced the severity of acute pancreatitis. Furthermore, we elucidated the molecular mechanisms underlying the lipotoxicity exerted by 1-deoxysphingolipids towards rodent pancreatic acinar cells in vitro.

RESULTS

We demonstrated that L-serine supplementation reduced the damage of acinar tissue resulting from the induction of pancreatitis in diabetic mice (average histological damage score: 1.5 in L-serine-treated mice vs 2.7 in the control group). At the cellular level, we showed that L-serine decreased the production of reactive oxygen species, endoplasmic reticulum stress and cellular apoptosis in acinar tissue. Importantly, these parameters, together with DNA damage, were triggered in acinar cells upon treatment with 1-deoxysphingolipids in vitro, suggesting that these lipids are cytotoxic towards pancreatic acinar cells in a cell-autonomous manner. In search of the initiating events of the observed cytotoxicity, we discovered that 1-deoxysphingolipids induced early mitochondrial dysfunction in acinar cells, characterised by ultrastructural alterations, impaired oxygen consumption rate and reduced ATP synthesis.

CONCLUSIONS/INTERPRETATION

Our results suggest that 1-deoxysphingolipids directly damage the functionality of pancreatic acinar cells and highlight that an L-serine-enriched diet may be used as a promising prophylactic intervention to reduce the severity of pancreatitis in the context of diabetes.

Altered nutrient status reprograms host inflammation and metabolic health via gut microbiota

The metabolism of macro- and micronutrients is a complex and highly regulated biological process. An imbalance in the metabolites and their signaling networks can lead to nonresolving inflammation and consequently to the development of chronic inflammatory-associated diseases. Therefore, identifying the accumulated metabolites and altered pathways during inflammatory disorders would not only serve as "real-time" markers but also help in the development of nutritional therapeutics. In this review, we explore recent research that has delved into elucidating the effects of carbohydrate/calorie restriction, protein malnutrition, lipid emulsions and micronutrient deficiencies on metabolic health and inflammation. Moreover, we describe the integrated stress response in terms of amino acid starvation and lipemia and how this modulates new age diseases such as inflammatory bowel disease and atherosclerosis. Lastly, we explain the latest research on metaflammation and inflammaging. This review focuses on multiple signaling pathways, including, but not limited to, the FGF21-β-hydroxybutryate-NLRP3 axis, the GCN2-eIF2α-ATF4 pathway, the von Hippel-Lindau/hypoxia-inducible transcription factor pathway and the TMAO-PERK-FoxO1 axis. Additionally, throughout the review, we explain how the gut microbiota responds to altered nutrient status and also how antimicrobial peptides generated from nutrient-based signaling pathways can modulate the gut microbiota. Collectively, it must be emphasized that metabolic starvation and inflammation are strongly regulated by both environmental (i.e., nutrition, gut microbiome) and nonenvironmental (i.e., genetics) factors, which can influence the susceptibility to inflammatory disorders.

Serine Deficiency Exacerbates Inflammation and Oxidative Stress via Microbiota-Gut-Brain Axis in D-Galactose-Induced Aging Mice

Inflammation and oxidative stress play key roles in the process of aging and age-related diseases. Since serine availability plays important roles in the support of antioxidant and anti-inflammatory defense system, we explored whether serine deficiency affects inflammatory and oxidative status in D-galactose-induced aging mice. Male mice were randomly assigned into four groups: mice fed a basal diet, mice fed a serine- and glycine-deficient (SGD) diet, mice injected with D-galactose and fed a basal diet, and mice injected with D-galactose and fed an SGD diet. The results showed that D-galactose resulted in oxidative and inflammatory responses, while serine deficiency alone showed no such effects. However, serine deficiency significantly exacerbated oxidative stress and inflammation in D-galactose-treated mice. The composition of fecal microbiota was affected by D-galactose injection, which was characterized by decreased microbiota diversity and downregulated ratio of Firmicutes/Bacteroidetes, as well as decreased proportion of Clostridium XIVa. Furthermore, serine deficiency exacerbated these changes. Additionally, serine deficiency in combination with D-galactose injection significantly decreased fecal butyric acid content and gene expression of short-chain fatty acid transporters (Slc16a3 and Slc16a7) and receptor (Gpr109a) in the brain. Finally, serine deficiency exacerbated the decrease of expression of phosphorylated AMPK and the increase of expression of phosphorylated NFκB p65, which were caused by D-galactose injection. In conclusion, our results suggested that serine deficiency exacerbated inflammation and oxidative stress in D-galactose-induced aging mice. The involved mechanisms might be partially attributed to the changes in the microbiota-gut-brain axis affected by serine deficiency.

Saikosaponin-d ameliorates dextran sulfate sodium-induced colitis by suppressing NF-κB activation and modulating the gut microbiota in mice

Saikosaponin-d (SSd), extracts from Bupleurum falcatum L, exhibits anti-inflammatory and anti-infectious activities. However, the effect of SSd on intestinal inflammation has not been investigated. The aim of this study was to evaluate the effect of SSd on dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) mice, and to elucidate the underlying mechanisms. UC was induced in mice by administrating 3% DSS in drinking water for 7 days. SSd (4 mg/kg and 8 mg/kg) was administered by gavage every day during the experimental process. The results showed that SSd treatment (8 mg/kg) significantly ameliorated UC mice by decreasing disease activity index (DAI), increasing colon length and improving pathological characteristics. SSd treatment (8 mg/kg) significantly suppressed the mRNA levels of pro-inflammatory cytokines including TNF-α, IL-6 and IL-1β, increased that of anti-inflammatory cytokine IL-10. Furthermore, SSd (8 mg/kg) suppressed the activation of NF-κB by decreasing the degradation and phosphorylation of IκB. SSd (8 mg/kg) also protected the intestinal barrier by increasing the mRNA levels of mucin (Muc1 and Muc2) and the protein levels of zonula occludens-1 (ZO-1) and Claudin-1. The 16S rDNA gene high-throughput sequencing revealed that SSd treatment (8 mg/kg) increased the alpha diversity and regulated the structure of gut microbiota in UC mice. Taken together, our findings demonstrated that SSd (8 mg/kg) improved DSS-induced intestinal inflammation by inhibiting NF-κB activation and regulated the gut microbiota.

Serine is required for the maintenance of redox balance and proliferation in the intestine under oxidative stress

Serine has critical roles in maintaining cell growth and redox balance in cancer cells. However, the role of exogenous serine played in oxidative response and proliferation in normal mammalian intestine need to be further elucidated. We used a mouse model and intestinal porcine epithelial cells (IPEC-J2) to reveal that exogenous serine deficiency did not lead to redox imbalance and inhibition of proliferation in the intestine. However, serine deficiency exacerbated oxidative stress, mitochondrial dysfunction, apoptosis, and inhibition of proliferation in IPEC-J2 cells challenged by hydrogen peroxide, while serine supplementation rescued redox imbalance and those proliferation defects. Importantly, serine supplementation restored the glutathione content and decreased the accumulation of reactive oxygen species, while no such effects were observed when glutathione synthesis was inhibited. Additionally, serine supplementation increased nuclear nrf2 expression in IPEC-J2 cells. These results suggested that serine alleviates oxidative stress through supporting glutathione synthesis and activating nrf2 signaling. We further found that serine supplementation activated the mTOR pathway, while inhibition of mTOR diminished the effects of serine on promoting proliferation, suggesting critical roles of the mTOR pathway in this context. Taken together, our study underlines the importance of serine in the maintenance of redox status and proliferation in the intestine and reveals a novel potential mechanism that mediates these effects.

Encapsulation of Escherichia coli strain Nissle 1917 in a chitosan-alginate matrix by combining layer-by-layer assembly with CaCl2 cross-linking for an effective treatment of inflammatory bowel diseases

Escherichia coli strain Nissle 1917 (EcN) has been widely shown to effectively treat inflammatory bowel diseases (IBDs). Unfortunately, after oral administration, EcN viability dramatically decreases due to severe environmental factors, including low gastric pH, temperature and osmotic pressure. To address these challenges and improve oral bio-availability, this study utilized layer-by-layer assembly (LbL) and ionic cross-linking with CaCl₂ as a method of EcN encapsulation (GEcN). Upon examination, GEcN cells were shown to maintain their ability to grow and proliferate, but had a slightly longer stationary phase (10 h) relative to free EcN (4 h). When exposed to simulated gastric fluid (SGF), a higher number of GEcN cells survived up to 12 h when compared to the other groups. To assess the therapeutic effect of EcN encapsulation in vivo, a TNBS-induced colitis rat model was established. When compared with the oral administration of free EcN, GEcN exhibited a significantly enhanced anti-inflammatory effect. Furthermore, GEcN treatment showed a lower disease activity index (DAI), decreased pro-inflammatory cytokine expression (MPO, TNF-α, IL-6) and increased anti-inflammatory cytokine expression (IL-10). Additionally, rats that received GEcN had much higher ZO-1 expression levels. These results suggest that EcN encapsulation in a chitosan-alginate matrix when utilizing the LbL assembly with CaCl₂ cross-linking can improve probiotic viability in a gastric environmental and thereby offer a more effective treatment for IBDs.

Taraxacum officinale extract ameliorates dextran sodium sulphate-induced colitis by regulating fatty acid degradation and microbial dysbiosis

Numerous data show that taraxacum officinale extract (TOE) exerts protective effects on inflammatory diseases. However, the underlying mechanisms by which TOE affects dextran sulphate sodium (DSS)-induced colitis remain unclear. After DSS-induced colitis were treated with different concentrations of TOE for 8 days, the bodyweight, disease activity index (DAI), colon lengths and pathological scoring were assessed, and histopathological examination was confirmed by HE staining. Furthermore, a transcriptome sequencing was performed by using the colon tissues between TOE and DSS groups, and the differentially expressed genes were conducted for the Kyoto Encyclopaedia of Genes and Genomes (KEGG) and gene set enrichment analysis (GSEA) and were validated by qRT-PCR and immunohistochemistry analysis. In addition, a 16S rDNA sequencing was carried out to distinguish the differential gut microbiota by using the mouse faecal samples between TOE and DSS groups. We found that TOE attenuated the clinical symptoms, lowered the inflammatory scoring and inhibited the secretion of proinflammatory factors TNF-α, IL-1β and IL-6 in DSS-induced colitis. KEGG and GSEA analysis demonstrated that fatty acid degradation and cytokine-receptor signalling were predominantly enriched in TOE-treated colitis as compared with the DSS group. Further investigations revealed that TOE increased the expression levels of Adh5, Aldh3a2 and Acox3, but decreased those of CCL20, CCR6 and CXCL1/5 in DSS-induced colitis, where TOE also induced the enrichment of S24-7 and adlercreutzia, but decreased the amount of anaerostipes, enterococcus, enterobacteriaceae and peptostreptococcaceae. In conclusion, TOE ameliorated DSS-induced colitis by regulating fatty acid degradation and microbial dysbiosis.

Pinocembrin Protects Against Dextran Sulfate Sodium-Induced Rats Colitis by Ameliorating Inflammation, Improving Barrier Function and Modulating Gut Microbiota

Pinocembrin (PIN) is a natural flavonoid widely found in bee propolis with potent gastrointestinal protective effects. In consequence, PIN has great potential in preventing inflammatory bowel diseases (IBDs) while scant information is available. In this study, a dextran sulfate sodium (DSS)-induced rats ulcerative colitis model (3.5% DSS in drinking water for 7 days) was applied to explore the protective effects of PIN on macroscopic colitis symptoms, inflammation, intestinal epithelial barrier function, and gut microbiota homeostasis. While DSS-treated rats showed severe colitis clinical symptoms and histological changes (colonic pathological damages and intestinal goblet cells loss), pre-administration of PIN (5 and 10 mg/kg, p.o.) for a week alleviated these symptoms. Pre-administration of PIN also suppressed the pro-inflammatory gene expressions and improved tight junction functions of colonic epithelial cells. Additionally, PIN administration reversed DSS-induced short chain fatty acid loss, and improved the gut microbial diversity assessed by 16S rRNA phylogenetic sequencing. Overall, our results suggest a wide spectrum of protective effects of PIN in preventing IBDs.

Effects of Blidingia sp. Extract on Intestinal Inflammation and Microbiota Composition in LPS-Challenged Mice

Blidingia sp. is a green alga that has spread rapidly in Subei Shoal, China. To explore the potential beneficial effects of Blidingia sp., we investigated the anti-inflammatory activity of its water–methanol extract of Blidingia sp. in a mouse model of lipopolysaccharide (LPS)-induced intestinal inflammation. The results revealed that the administration of Blidingia extract significantly alleviated the LPS-induced increase of the inflammatory cytokine content in the serum, as well as latter’s gene expression in the ileum. Moreover, the extract inhibited the phosphorylation of NF-κB and IκBα in LPS-challenged mice. Apart from these changes, the extract also averted intestinal morphology damage(s) and cell apoptosis in mice. Interestingly, the extract also had beneficial effects on the diversity and composition of caecal microbiota in LPS-challenged mice. In conclusion, the results suggested that Blidingia extract had beneficial effects on the recovery of intestinal function by reducing the inflammatory response, improving the maintenance of intestinal morphology, and decreasing cell apoptosis in LPS-induced intestinal inflammation. In addition, the beneficial effects of the extract on caecal microbiota composition may play a role in its anti-inflammatory activity. These results suggested that Blidingia extract could be potentially used in preventing intestinal inflammation.