Probiotic strains alleviated OVA-induced food allergy in mice by regulating the gut microbiota and improving the level of indoleacrylic acid in fecal samples

Phage cocktail alleviated type 2 diabetes by reshaping gut microbiota and decreasing proinflammatory cytokines

Type 2 diabetes (T2D), a global health concern, is closely associated with the gut microbiota. Restoration of a balanced microbiota and intestinal homeostasis benefit therapy of T2D. Some special phages may selectively alter the gut microbiota without causing dysbiosis, such as MS2 and P22. However, scarcely systematic analysis of cascading effects triggered by MS2 and P22 phages on the microbiota, as well as interactions between specific gut bacteria and systemic metabolism, seriously inhibit the development of positive interventions of phages. Based on multi-omic analysis, we analyzed the intrinsic correlations among specific microbiota, their bioactive metabolites, and key indicators of T2D. We found that gavage of the MS2-P22 phage cocktail could significantly alter the gut microbiome to attenuate dysbiosis of diabetic C57BL/6 mice caused by high-fat diets (HFDs) and streptozotocin (STZ), by affecting microbial compositions as well as their metabolic pathways and metabolites, especially increasing amounts of short-chain fatty acid-producing (SCFA-producing) bacteria (e.g., Blautia and Romboutsia) and short-chain fatty acids (SCFAs). Correspondingly, a noteworthy reduction in the number of several opportunistic pathogens occurred, e.g., Candidatus Saccharimonas, Aerococcus, Oscillibacter, Desulfovibrio, and Clostridium sensu stricto 1. Synchronously, the levels of proinflammatory cytokines and lipopolysaccharide (LPS) were reduced to recover gut barrier function in T2D mice. These findings might benefit the development of a new dietary intervention for T2D based on phage cocktails. KEY POINTS: • Intestinal barrier integrity of T2D mice is improved by a phage cocktail • Negative relationship between Muribaculaceae and Corynebacterium reshaped gut microbiota • Acetate, propionate, and butyrate decreased the level of proinflammatory factors.

Investigating the effects of radiation, T cell depletion, and bone marrow transplantation on murine gut microbiota

Microbiome research has gained much attention in recent years as the importance of gut microbiota in regulating host health becomes increasingly evident. However, the impact of radiation on the microbiota in the murine bone marrow transplantation model is still poorly understood. In this paper, we present key findings from our study on how radiation, followed by bone marrow transplantation with or without T cell depletion, impacts the microbiota in the ileum and caecum. Our findings show that radiation has different effects on the microbiota of the two intestinal regions, with the caecum showing increased interindividual variation, suggesting an impaired ability of the host to regulate microbial symbionts, consistent with the Anna Karenina principle. Additionally, we observed changes in the ileum composition, including an increase in bacterial taxa that are important modulators of host health, such as Akkermansia and Faecalibaculum. In contrast, radiation in the caecum was associated with an increased abundance of several common commensal taxa in the gut, including Lachnospiraceae and Bacteroides. Finally, we found that high doses of radiation had more substantial effects on the caecal microbiota of the T-cell-depleted group than that of the non-T-cell-depleted group. Overall, our results contribute to a better understanding of the complex relationship between radiation and the gut microbiota in the context of bone marrow transplantation and highlight the importance of considering different intestinal regions when studying microbiome responses to environmental stressors.

Gut Microbiota-Derived Tryptophan Metabolites Alleviate Allergic Asthma Inflammation in Ovalbumin-Induced Mice

Asthma is a prevalent respiratory disease. The present study is designed to determine whether gut microbiota-derived tryptophan metabolites alleviate allergic asthma inflammation in ovalbumin (OVA)-induced mice and explore the effect and potential mechanism therein. Asthma model mice were constructed by OVA treatment, and kynurenine (KYN), indole-3-lactic acid (ILA), in-dole-3-carbaldehyde (I3C), and indole acetic acid (IAA) were administered by intraperitoneal injection. The percent survival, weight and asthma symptom score of mice were recorded. The total immunoglobulin E and OVA-specific (s)IgE in the serum and the inflammatory cytokines in the bronchoalveolar lavage fluid (BALF) were detected by the corresponding ELISA kits. The composition of the gut microbiota and tryptophan-targeted metabolism in mouse feces were analyzed using 16S rRNA gene sequencing and targeted metabolomics, respectively. The four tryptophan metabolites improved the percent survival, weight and asthma symptoms of mice, and reduced the inflammatory cells in lung tissues, especially I3C. I3C and IAA significantly (p < 0.05) downregulated the levels of OVA-IgE and inflammatory cytokines. KYN was observed to help restore gut microbiota diversity. Additionally, I3C, KYN, and ILA increased the relative abundance of Anaeroplasma, Akkermansia, and Ruminococcus_1, respectively, which were connected with tryptophan metabolic pathways. IAA also enhanced capability of tryptophan metabolism by the gut microbiota, restoring tryptophan metabolism and increasing production of other tryptophan metabolites. These findings suggest that tryptophan metabolites may modulate asthma through the gut microbiota, offering potential benefits for clinical asthma management.

Lactobacillus rhamnosus Probio-M9 alleviates OVA-sensitized food allergy through modulating gut microbiota and its metabolism

Over the past few decades, food allergy has continued to rise, significantly affecting our health, economy, and quality of life. However, current therapeutic strategies have limited efficacy and need to be improved. One alternative to prevent or reduce allergies is to modulate immunity and microbiota. Human milk (HM) could be considered a protective factor against food allergy, but how probiotics in human milk impact the susceptibility to food allergy remains unknown. Therefore, we studied the preventive impact of human milk Lactobacillus rhamnosus Probio-M9 on food allergy in ovalbumin (OVA)-sensitized mice. We studied the effects of oral administration of Probio-M9 on allergic signatures, immune response, gut microbiota, and metabolism. Oral therapeutic administration of live Probio-M9, but not heat-killed Probio-M9, significantly reduces OVA-specific IgE (OVA-sIgE), histamine, and mMCP-1 (mouse mast cell protease-1) levels in OVA-sensitized mice. Moreover, Probio-M9 supplementation reduced allergic inflammation and changes in the Th2/Th1 balance toward a dampened Th2 response. 16S rDNA sequencing analysis revealed an increased ratio of Firmicutes/Bacteroidota (F/B) and the relative abundance of short-chain fatty acid (SCFA)-producing Clostridia in the feces after Probio-M9 intake. Simultaneously, Probio-M9 significantly increased the levels of SCFAs and promoted the phosphorylation of signal transducer and activator of transcription 3 (STAT3), thereby inducing the expression of the antimicrobial peptides (AMPs) Reg3b and Reg3g. Our findings suggest that the use of Probio-M9 can be a potent strategy in food allergy prevention.

Early-life gut microbiota in food allergic children and its impact on the development of allergic disease

BACKGROUND

The prevalence of food allergies (FA) has been steadily increasing over 2 to 3 decades, showing diverse symptoms and rising severity. These long-term outcomes affect children's growth and development, possibly linking to inflammatory bowel disease. However, the cause remains unclear. Previous studies reveal that early infancy significantly impacts FA development through gut microbiota. Yet, a consistent view on dysbiosis characteristics and its connection to future allergies is lacking. We explored how early-life gut microbiota composition relates to long-term clinical signs in children with FA through longitudinal research.

METHODS

We employed high-throughput 16S rDNA gene sequencing to assess gut microbiota composition in early-life FA children in southern Zhejiang. Follow-up of clinical manifestations over 2 years allowed us to analyze the impact of early-life gut microbiota dysbiosis on later outcomes.

RESULTS

While the diversity of gut microbiota in FA children remained stable, there were shifts in microbiota abundance. Abundant Akkermansia, Parabacteroides, Blautia, and Escherichia-Shigella increased, while Bifidobacterium and Clostridium decreased. After 2 years, two of ten FA children still showed symptoms. These two cases exhibited increased Escherichia-Shigella and reduced Bifidobacterium during early childhood. The other eight cases experienced symptom remission.

CONCLUSIONS

Our study suggests that FA and its prognosis might not correlate with early-life gut microbiota diversity. Further experiments are needed due to the small sample size, to confirm these findings.

Short-chain fatty acid - A critical interfering factor for allergic diseases

Allergy is a growing global public health problem with a high socio-economic impact. The incidence of allergic diseases is increasing year by year, which has attracted more and more attention. In recent years, a number of epidemiological investigations and gut microbiota studies have shown that gut microbiota dysbiosis is associated with an increased prevalence of various allergic diseases, such as food allergy, asthma, allergic rhinitis, and atopic dermatitis. However, the underlying mechanisms are complex and have not been fully clarified. Metabolites are one of the main ways in which the gut microbiota functions. Short-chain fatty acids (SCFAs) are the main metabolites of intestinal flora fermentation and are beneficial to human health. Studies have shown that SCFAs play an important role in maintaining intestinal homeostasis and regulating immune responses by recognizing receptors and inhibiting histone deacetylases, and are key molecules involved in the occurrence and development of allergic diseases. In addition, research on the regulation of gut microbiota and the application of SCFAs in the treatment of allergic diseases is also emerging. This article reviews the clinical and experimental evidence on the correlation between SCFAs and allergic diseases and the potential mechanisms by which SCFAs regulate allergic diseases. Furthermore, SCFAs as therapeutic targets for allergic diseases are also summarized and prospected.

Leuconostoc mesenteroides WHH1141 ameliorates ovalbumin-induced food allergy in mice

Food allergy (FA) is acknowledged as a significant public health and food safety issue, due to its manifestation as an amplified immune reaction to food antigens. Recently, probiotics within Lactobacillus and Bifidobacterium have been highlighted as a promising strategy against allergic disease by modulating the balance of Th1/Th2 responses. However, the allergy-alleviating effects of probiotic Leuconostoc mesenteroides strains are unknown. Therefore, this study investigated the potentials of eleven L. mesenteroides strains on the Th1/Th2 balance in vitro by evaluating the expression patterns of interferon-gamma (IFN-γ) (Th1 cytokine) and interleukin-4 (IL-4) (Th2 cytokine) in mesenteric lymph node-derived lymphocytes from ovalbumin (OVA)-sensitized mice. Among strains, WHH1141 incubation caused the highest IFN-γ/IL-4 ratio. Oral administration of WHH1141 (1 × 109  CFU/mL) in the OVA-induced FA mouse model for 40 days improved the weight loss and FA pathological symptoms and normalized the serum immunoglobulin E levels. Meanwhile, the OVA-induced elevated gene expressions of cytokines (IL-4, IL-5, and IL-13) and tight-junction proteins (ZO-1 and Occludin) and levels of cytokines (IL-4, IL-5, and IL-13) and histamine in the jejunum were restored by WHH1141. Furthermore, WHH1141 reversed the reduced gut microbial diversity and short-chain fatty acid (SCFA) levels, specifically increased Bacteroidota abundance, and decreased Firmicutes abundance in OVA-induced mice. Overall, these findings suggest that WHH1141 exerts FA-alleviating effects on OVA-induced mice, which is involved with the inhibition of the jejunal Th2 immune responses and the modulation of gut microbiome composition and SCFA productions. PRACTICAL APPLICATION: Leuconostoc mesenteroides WHH1141 with FA-alleviating potentials may be considered a promising approach in the mitigation of FA symptoms.

Combination of Gut Microbial Features and the Proteomic Pattern Revealed Changes in Specific Intestinal Luminal Factors and Mechanisms of Their Regulation of Gluten Allergy

Recent research consensus has highlighted the role of intestinal luminal factors in the association between intestinal microenvironment homeostasis and food allergy. However, the association between intestinal immune homeostasis and food allergy-related proteomic features remains elusive. In this study, we aimed to investigate the changes in gluten allergy (GA)-defined phenotypes and endotypes and intestinal microenvironment factors in BALB/c mice and linked GA to colonic proteomic signatures. Combined with increased allergy and diarrhea scores, intense antibody responses and abnormalities in T-cell cytokine production were induced in mice. GA-associated disruption of intestinal microenvironment homeostasis was underlined by the increased colonic pH, decreased intestinal antioxidant capacity, impaired intestinal barrier function, and decreased production and imbalanced proportions of short-chain fatty acids. 16S rRNA amplicon sequencing showed that the gut microbiota dysbiosis in mice was characterized by significant enrichment of six bacterial taxonomic units, including Prevotellaceae, Escherichia Shigella, Alloprevotella, Escherichia coli, Bacteroides vulgatus, and Lachnospiraceae bacterium DW59, which was correlated with immune end points. Using a label-free proteomics quantitative approach, 24 differentially expressed proteins linking GA-induced gut dysbiosis were identified, with four of them enriched in the serine endopeptidase inhibitor activity pathway. The development of GA in mice was associated with changes in specific intestinal luminal factors and may be mediated by serine protease activity-associated metabolic routes.

Modulation of immunity by tryptophan microbial metabolites

Tryptophan (Trp) is an essential amino acid that can be metabolized via endogenous and exogenous pathways, including the Kynurenine Pathway, the 5-Hydroxyindole Pathway (also the Serotonin pathway), and the Microbial pathway. Of these, the Microbial Trp metabolic pathways in the gut have recently been extensively studied for their production of bioactive molecules. The gut microbiota plays an important role in host metabolism and immunity, and microbial Trp metabolites can influence the development and progression of various diseases, including inflammatory, cardiovascular diseases, neurological diseases, metabolic diseases, and cancer, by mediating the body's immunity. This review briefly outlines the crosstalk between gut microorganisms and Trp metabolism in the body, starting from the three metabolic pathways of Trp. The mechanisms by which microbial Trp metabolites act on organism immunity are summarized, and the potential implications for disease prevention and treatment are highlighted.

Clostridium butyricum Reduces Obesity in a Butyrate-Independent Way

Accumulating evidence from recent studies links the gut microbiota to obesity, and microbiome therapy has been examined as a treatment. Clostridium butyricum (C. butyricum), an intestinal symbiont, protects the host from a range of diseases. Studies have shown a negative correlation between the relative abundance of C. butyricum and a predisposition for obesity. However, the physiological function and material basis of C. butyricum for obesity are unclear. Here, five C. butyricum isolates were administered to mice on a high-fat diet (HFD) to determine their anti-obesity effects. All isolates suppressed the formation and inflammation of subcutaneous fat, and the two effective strains considerably reduced weight gain and ameliorated dyslipidemia, hepatic steatosis, and inflammation. These positive effects were not achieved by increasing the concentration of intestinal butyrate, and the effective strains could not be replaced by sodium butyrate (NaB). We also discovered that oral supplementation with the two most effective strains changed the metabolism of tryptophan and purine and altered the composition of the gut microbiota. In summary, C. butyricum improved the metabolic phenotypes under the HFD by controlling the composition of the gut microbiota and modulating intestinal metabolites, thereby demonstrating its ability to fight obesity and providing a theoretical foundation for microbial preparations production.

Gut microbiome modulation by probiotics, prebiotics, synbiotics and postbiotics: a novel strategy in food allergy prevention and treatment

Food allergy has caused lots of global public health issues, particularly in developed countries. Presently, gut microbiota has been widely studied on allergy, while the role of dysbiosis in food allergy remains unknown. Scientists found that changes in gut microbial compositions and functions are strongly associated with a dramatic increase in the prevalence of food allergy. Altering microbial composition is crucial in modulating food antigens' immunogenicity. Thus, the potential roles of probiotics, prebiotics, synbiotics, and postbiotics in affecting gut bacteria communities and the immune system, as innovative strategies against food allergy, begins to attract high attention of scientists. This review briefly summarized the mechanisms of food allergy and discussed the role of the gut microbiota and the use of probiotics, prebiotics, synbiotics, and postbiotics as novel therapies for the prevention and treatment of food allergy. The perspective studies on the development of novel immunotherapy in food allergy were also described. A better understanding of these mechanisms will facilitate the development of preventive and therapeutic strategies for food allergy.

L-Theanine Modulates Intestine-Specific Immunity by Regulating the Differentiation of CD4+ T Cells in Ovalbumin-Sensitized Mice

Ovalbumin (OVA), a common food protein, can cause deadly allergies with intestine-specific immune reactions. L-Theanine (LTA) shows great potential for regulating intestinal immunity. To investigate the regulatory effect of LTA intervention on intestine-specific immunity, a 41 day experiment was performed on BALB/c OVA-sensitized mice. The results show that injecting female mice intraperitoneally with 50 μg of OVA and administering 30 mg of OVA 4 times can successfully establish an OVA-sensitized mouse model. LTA intervention significantly increased weight gain and thymus index (p < 0.05), decreased allergy and diarrhea scores (p < 0.05), and improved jejunum structure. Meanwhile, the histological score and degranulation of mast cells decreased. LTA intervention increased Clostridiales, Lachnospiraceae, Lactobacillus, Prevotella, and Ruminococcus abundance while decreasing Helicobacter abundance. Flow cytometry and Western blotting results indicated that 200 and 400 mg/kg of LTA upregulated the expression of T-bet and Foxp3 proteins (p < 0.05), thus promoting the differentiation of jejunum CD4+ T cells to Th1 and Tregs and increasing the cytokines IFN-γ, IL-10, and TGF-β (p < 0.05). We found that 200 and 400 mg/kg of LTA downregulated the expression of RORγt and GATA3, thus inhibiting the differentiation of Th2 and Th17 cells and decreasing cytokines IL-4, IL-5, IL-13 TNF-α, IL-6, and IL-17A (p < 0.05). LTA inhibited the degranulation of mast cells and significantly decreased the serum levels of OVA-IgE, HIS, and mouse MCPT-1 (p < 0.05). Therefore, LTA intervention alleviated OVA allergy by improving intestine-specific immunity.

Novel perspective on the regulation of food allergy by probiotic: The potential of its structural components

Food allergy (FA) is a global public health issue with growing prevalence. Increasing evidence supports the strong correlation between intestinal microbiota dysbiosis and food allergies. Probiotic intervention as a microbiota-based therapy could alleviate FA effectively. In addition to improving the intestinal microbiota disturbance and affecting microbial metabolites to regulate immune system, immune responses induced by the recognition of pattern recognition receptors to probiotic components may also be one of the mechanisms of probiotics protecting against FA. In this review, it is highlighted in detail about the regulatory effects on the immune system and anti-allergic potential of probiotic components including the flagellin, pili, peptidoglycan, lipoteichoic acid, exopolysaccharides, surface (S)-layer proteins and DNA. Probiotic components could enhance the function of intestinal epithelial barrier as well as regulate the balance of cytokines and T helper (Th) 1/Th2/regulatory T cell (Treg) responses. These evidences suggest that probiotic components could be used as nutritional or therapeutic agents for maintaining immune homeostasis to prevent FA, which will contribute to providing new insights into the resolution of FA and better guidance for the development of probiotic products.

Strategies for the Identification and Assessment of Bacterial Strains with Specific Probiotic Traits

Early in the 1900s, it was proposed that health could be improved and senility delayed by manipulating gut microbiota with the host-friendly bacteria found in yogurt. Later, in 1990, the medical community reconsidered this idea and today probiotics represent a developed area of research with a billion-dollar global industry. As a result, in recent decades, increased attention has been paid to the isolation and characterization of novel probiotic bacteria from fermented foods and dairy products. Most of the identified probiotic strains belong to the lactic acid bacteria group and the genus Bifidobacterium. However, current molecular-based knowledge has allowed the identification and culture of obligatory anaerobic commensal bacteria from the human gut, such as Akkermansia spp. and Faecalibacterium spp., among other human symbionts. We are aware that the identification of new strains of these species does not guarantee their probiotic effects and that each effect must be proved through in vitro and in vivo preclinical studies before clinical trials (before even considering it as a probiotic strain). In most cases, the identification and characterization of new probiotic strain candidates may lack the appropriate set of in vitro experiments allowing the next assessment steps. Here, we address some innovative strategies reported in the literature as alternatives to classical characterization: (i) identification of alternatives using whole-metagenome shotgun sequencing, metabolomics, and multi-omics analysis; and (ii) probiotic characterization based on molecular effectors and/or traits to target specific diseases (i.e., inflammatory bowel diseases, colorectal cancer, allergies, among others).