Friend or foe? Lactobacillus in the context of autoimmune disease

Therapeutic Evaluation of Bifidobacterium animalis subsp. lactis MH-02 as an Adjunctive Treatment in Patients with Reflux Esophagitis: A Randomized, Double-Blind, Placebo-Controlled Trial

Proton pump inhibitors (PPIs) are currently routinely used for the treatment of reflux esophagitis (RE); however, with frequent symptom recurrence after discontinuation and limited clinical improvement in accompanying gastrointestinal symptoms. This study aims to explore the adjuvant therapeutic effect of Bifidobacterium supplement for RE patients. A total of 110 eligible RE patients were recruited and randomly assigned to the placebo and probiotic groups. All patients were treated with rabeprazole tablets and simultaneously received either Bifidobacterium animalis subsp. lactis MH-02 or placebo for 8 weeks. Patients who achieved clinical remission then entered the next 12 weeks of follow-up. RDQ, GSRS scores, and endoscopy were performed to assess clinical improvement, and changes in intestinal microbiota were analyzed with high-throughput sequencing. Our results revealed that MH-02 combined therapy demonstrated an earlier time to symptom resolution (50.98% vs. 30.61%, p = 0.044), a significant reduction in the GSRS score (p = 0.0007), and a longer mean time to relapse (p = 0.0013). In addition, high-throughput analyses showed that MH-02 combined therapy increased the α (p = 0.001) diversity of gut microbiota and altered microbial composition by beta diversity analysis, accompanied with significantly altered gut microbiota taxa at the genus level, where the abundance of some microbial genera including Bifidobacterium, Clostridium, and Blautia were increased, while the relative abundance of Streptococcus and Rothia were decreased (p < 0.05). Collectively, these results support the beneficial effects of MH-02 as a novel complementary strategy in RE routine treatment.

Relationship between gut microbiota and vascular calcification in hemodialysis patients

INTRODUCTION

Vascular calcification (VC) is an independent risk factor for cardiovascular mortality in end-stage renal disease (ESRD) patients. The pathogenesis of VC is complicated and unclear. Uremic toxins produced by gut microbiota can promote VC. This study aims to identify the differences in gut microbiota between the different VC groups and the main bacteria associated with VC in hemodialysis (HD) patients in an attempt to open up new preventive and therapeutic approaches and define the probable mechanism for VC in HD patients in the future.

METHODS

A total of 73 maintenance HD patients were enrolled in this cross-sectional study. According to the abdominal aortic calcification (AAC) scores, the participants were divided into the high AAC score group and the low AAC score group. High-throughput sequencing of the gut microbiota was performed and the results were evaluated by alpha diversity, beta diversity, species correlation, and model predictive analyses.

RESULTS

The prevalence of VC was 54.79% (40/73) in the study. The majority of phyla in the two groups were the same, including Firmicutes, Actinobacteriota, Proteobacteria, and Bacteroidota. The microbial diversity in the high AAC score group had a decreasing trend (p = 0.050), and the species abundance was significantly lower (p = 0.044) than that in the low AAC score group. The HD patients with high AAC scores showed an increased abundance of Proteobacteria and decreased abundances of Bacteroidota and Synergistota at the phylum level; increased abundances of Escherichia-Shigella, Ruminococcus_gnavus_group, and Lactobacillus; and decreased abundances of Ruminococcus and Lachnospiraceae_NK4A136_group at the genus level (p<0.05). Escherichia-Shigella and Ruminococcus_gnavus_group were positively correlated with VC, and Ruminococcus, Adlercreutzia, Alistipes, and norank_f__Ruminococcaceae were negatively correlated with VC. Escherichia-Shigella had the greatest influence on VC in HD patients, followed by Ruminococcus and Butyricimonas.

CONCLUSIONS

Our results provide clinical evidence that there was a difference in gut microbiota between the different VC groups in HD patients. Escherichia-Shigella, a lipopolysaccharide (LPS)-producing bacterium, was positively correlated with VC and had the greatest influence on VC. Ruminococcus, a short-chain fatty acid (SCFA)-producing bacterium, was negatively correlated with VC and had the second strongest influence on VC in HD patients. The underlying mechanism is worth studying. These findings hint at a new therapeutic target.

Too Much of a Good Thing: Extended Duration of Gut Microbiota Depletion Reverses Protection From Experimental Autoimmune Uveitis

Purpose

Using the model of experimental autoimmune uveitis (EAU) induced by immunization with a retinal antigen, two studies have reported contradictory results on disease development following oral antibiotic treatment (ABX). We showed that long-term ABX did not affect EAU, but another study showed that short-term ABX was protective. We therefore studied the effects of ABX on EAU, gut microbiota, and host immune responses as a function of treatment duration.

Methods

EAU-susceptible mice were treated orally with broad-spectrum antibiotics starting at least 10 weeks (long-term) or 1 week (short-term) before immunization until termination of the experiment. Gut microbiota were characterized by 16S amplicon sequencing, and host gut immune elements were studied phenotypically and functionally.

Results

Long-term ABX had no effect, whereas short-term ABX delayed EAU, as previously reported by us and others, respectively. Microbial sequencing revealed progressive reduction of gut microbiota that showed some differences in the two ABX groups. Interestingly, duration of ABX was associated with a gradual disappearance of the CD4+ and CD4+CD8+ subset of gut intraepithelial lymphocytes (IELs). This IEL subset is microbiota dependent and is absent in germ-free mice. Relative abundance of Lactobacillus reuteri correlated with the frequencies of CD4+CD8+ IELs. IELs suppressed antigen-specific activation of autoreactive T cells in culture.

Conclusions

Gut microbiota may play dual roles in uveitis development: They promote EAU development but also help maintain IEL populations that have regulatory function against autoreactive T cells. We propose that the progressive loss of this population during long-term ABX reverses the EAU-ameliorating effects of microbiota depletion.

Lactobacillus Plantarum NC8 and its metabolite acetate alleviate type 1 diabetes via inhibiting NLRP3

A healthy organism is the result of host-microbiome co-evolution. Microbial metabolites can also stimulate immune cells to reduce intestinal inflammation and permeability. Gut dysbiosis will lead to a variety of autoimmune diseases, such as Type 1 diabetes (T1D). Most of probiotics, such as Lactobacillus casei, Lactobacillus reuteri, Bifidobacterium bifidium, and Streptococcus thermophiles, can improve the intestinal flora structure of the host, reduce intestinal permeability, and relieve symptoms of T1D patients if ingested above probiotics in sufficient amounts. Lactobacillus Plantarum NC8, a kind of Lactobacillus, whether it has an effect on T1D, and the mechanism of it regulating T1D is still unclear. As a member of the inflammatory family, NLRP3 inflammasome can enhance inflammatory responses by promoting the production and secretion of proinflammatory cytokines. Many previous studies had shown that NLRP3 also plays an important role in the development of T1D. When the NLRP3 gene is deleted, the disease progression of T1D will be delayed. Therefore, this study investigated whether Lactobacillus Plantarum NC8 can alleviate T1D by regulating NLRP3. The results demonstrated that Lactobacillus Plantarum NC8 and its metabolites acetate play a role in T1D by co-modulating NLRP3. Lactobacillus Plantarum NC8 and acetate can reduce the damage of T1D in the model mice, even if orally administered them in the early stage of T1D. The number of Th1/Th17 cells in the spleen and pancreatic lymph nodes (PLNs) of T1D mice were significantly reduced by oral Lactobacillus Plantarum NC8 or acetate. The expression of NLRP3 in the pancreas of T1D mice or murine macrophages of inflammatory model were significantly inhibited by treatment with Lactobacillus Plantarum NC8 or acetate. In addition, the number of macrophages in the pancreas were significantly reduced by the treatment with Lactobacillus Plantarum NC8 or acetate. In summary, this study indicated that the regulatory mechanism of Lactobacillus Plantarum NC8 and its metabolite acetate to T1D maybe via inhibiting NLRP3 and provides a novel insights into the mechanism of the alleviated role of probiotics to T1D.

Insights into Nutritional Strategies in Psoriasis

Psoriasis, an autoimmune chronic inflammatory skin condition, has a high incidence in the general population, reaching 2-4%. Its pathogenesis involves an interplay of genetic factors, immune disturbances, and environmental factors. Within the environmental factors that aid the appearance of this autoimmune skin disease, the Western lifestyle and overall diet play important roles in the steady growth in psoriasis prevalence. Furthermore, psoriasis is associated with comorbidities such as psoriatic arthritis, cardiovascular disease, metabolic syndrome, and obesity. Accumulating evidence suggests that obesity is an important risk factor for psoriasis. Moreover, obesity aggravates established psoriasis, and a reduction in the body mass index can improve the clinical outcomes of psoriasis and increase the efficacy of standard psoriasis therapies. The possible connection between this autoimmune disease and obesity relies on the fact that white adipose tissue is an essential endocrine organ that secretes an array of immune mediators and inflammatory and metabolic factors with pro-inflammatory action. Thus, immune-mediated mechanisms in both psoriasis and obesity conditions are common factors. This paper describes the factors that link obesity with skin autoimmune disease and highlights the importance of the stimulatory or regulatory effects of nutrients and food in psoriasis and the possible improvement of psoriasis through nutritional strategies.

Lactobacillus paracasei L9 affects disease progression in experimental autoimmune neuritis by regulating intestinal flora structure and arginine metabolism

BACKGROUND

Autoimmune neuropathies are common peripheral nervous system (PNS) disorders. Environmental influences and dietary components are known to affect the course of autoimmune diseases. Intestinal microorganisms can be dynamically regulated through diet, and this study combines intestinal microorganisms with diseases to open up new therapeutic ideas.

METHODS

In Lewis rats, a model of EAN was established with P0 peptide, Lactobacillus were used as treatment, serum T-cell ratio, inflammatory factors, sciatic neuropathological changes, and pathological inflammatory effects on intestinal mucosa were detected, and fecal metabolomics and 16 s microbiome analysis were performed to further explore the mechanism.

RESULTS

In the EAN rat model, Lactobacillus paracasei L9 (LP) could dynamically regulate the CD4⁺/CD8⁺T balance in serum, reduce serum IL-1, IL-6 and TNF-α expression levels, improve sciatic nerve demyelination and inflammatory infiltration, and reduce nervous system score. In the rat model of EAN, intestinal mucosa was damaged. Occludin and ZO-1 were downregulated. IL-1, TNF-α and Reg3γ were upregulated. LP gavage induced intestinal mucosa recovery; occludin and ZO-1 upregulation; IL-1, TNF-α and Reg3γ downregulation. Finally, metabolomics and 16 s microbiome analysis were performed, and differential metabolites were enriched with an important metabolic pathway, arginine and proline metabolism.

CONCLUSION

LP improved EAN in rats by influencing intestinal community and the lysine and proline metabolism.

Interplay of the microbiome and antifungal therapy in recurrent vulvovaginal candidiasis (RVVC): A narrative review

Recurrent vulvovaginal candidiasis (RVVC) is a microbial, immune and sexual health disorder impacting up to 10 % of the adult female population. Fluconazole is a well-established antifungal drug commonly utilized for acute and long-term RVVC treatment. This insight review provides an overview of known vaginal and gastrointestinal microbiota characteristics in RVVC, presents the potential impacts of fluconazole therapy on multi-microbiome relationships and discusses implications for future research and clinical practice. Next-generation sequencing (NGS) and molecular methods to accurately define vaginal microbiota trends in RVVC are not comprehensively available, limiting understanding of microbiota roles in RVVC. Inconsistencies and variances in Lactobacillus profiles in RVVC women suggest poorly understood disease implications on the bacterial and fungal microbiomes. Investigations of environmental conditions like vaginal pH, drug therapy's impact, especially fluconazole maintenance therapy, and the elucidation of multi-microbiome relationships in RVVC are required to further investigate disease pathogenesis and responsible antimicrobial prescribing.

Oral Lactoferrin Supplementation during Induction Chemotherapy Promotes Gut Microbiome Eubiosis in Pediatric Patients with Hematologic Malignancies

Induction chemotherapy is the first-line treatment for pediatric patients with hematologic malignancies. However, several complications may arise, mainly infections and febrile neutropenia, with a strong impact on patient morbidity and mortality. Such complications have been shown to be closely related to alterations of the gut microbiome (GM), making the design of strategies to foster its eubiosis of utmost clinical importance. Here, we evaluated the impact of oral supplementation of lactoferrin (LF), a glycoprotein endowed with anti-inflammatory, immunomodulatory and antimicrobial activities, on GM dynamics in pediatric oncohematologic patients during induction chemotherapy. Specifically, we conducted a double blind, placebo-controlled trial in which GM was profiled through 16S rRNA gene sequencing before and after two weeks of oral supplementation with LF or placebo. LF was safely administered with no adverse effects and promoted GM homeostasis by favoring the maintenance of diversity and preventing the bloom of pathobionts (e.g., Enterococcus). LF could, therefore, be a promising adjunct to current therapeutic strategies in these fragile individuals to reduce the risk of GM-related complications.

Amyloid-containing biofilms and autoimmunity

Bacteria are microscopic, single-celled organisms known for their ability to adapt to their environment. In response to stressful environmental conditions or in the presence of a contact surface, they commonly form multicellular aggregates called biofilms. Biofilms form on various abiotic or biotic surfaces through a dynamic stepwise process involving adhesion, growth, and extracellular matrix production. Biofilms develop on tissues as well as on implanted devices during infections, providing the bacteria with a mechanism for survival under harsh conditions including targeting by the immune system and antimicrobial therapy. Like pathogenic bacteria, members of the human microbiota can form biofilms. Biofilms formed by enteric bacteria contribute to several human diseases including autoimmune diseases and cancer. However, until recently the interactions of immune cells with biofilms had been mostly uncharacterized. Here, we will discuss how components of the enteric biofilm produced in vivo, specifically amyloid curli and extracellular DNA, could be interacting with the host's immune system causing an unpredicted immune response.

Oral dextran sulfate sodium administration induces peripheral spondyloarthritis features in SKG mice accompanied by intestinal bacterial translocation and systemic Th1 and Th17 cell activation

BACKGROUND

Spondyloarthritis (SpA) is an autoimmune and autoinflammatory musculoskeletal disease characterised by systemic enthesitis. Recent research has focused on subclinical inflammatory bowel disease (IBD) in SpA pathogenesis. SKG mice, harbouring the Zap70 W163C mutation, increase autoreactive Th17 cells intrinsically, and in a conventional environment, they exhibit spontaneous arthritis with fungal factors. Under SPF conditions, they show SpA features, including enteritis, after peritoneal injection of β-1,3-glucan. This study aimed to clarify whether oral dextran sulfate sodium (DSS) administration, utilised in IBD model mice, can provoke SpA features in SKG mice under SPF conditions, focusing on the relationship between gut microorganisms and SpA pathogenesis.

METHODS

BALB/c and SKG mice were administered oral DSS, and their body weights, arthritis, and enthesitis scores were recorded. In another cohort, antibiotics (meropenem and vancomycin) or an anti-fungal agent (amphotericin B) was administered orally before DSS administration. The splenic Th1 and Th17 cell populations were examined before and after DSS administration using flow cytometry. Furthermore, the amount of circulating bacterial DNA in whole blood was measured by absolute quantitative polymerase chain reaction (qPCR), and the number and characteristics of bacterial species corresponding to these circulating DNA were analysed by next-generation sequencing (NGS).

RESULTS

Ankle enthesitis as a peripheral SpA feature was elicited in half of DSS-administered SKG mice, and none of the BALB/c mice. Pre-administration of antibiotics suppressed enthesitis, whilst an anti-fungal agent could not. Th1 and Th17 cell levels in the spleen increased after DSS administration, and this was suppressed by pre-administration of antibiotics. SKG mice have a larger amount of bacterial DNA in whole blood than BALB/c mice before and 1 day after the initiation of DSS administration. The number of bacterial species in whole blood increased after DSS administration in BALB/c and SKG mice. Some genera and species significantly specific to the DSS-treated SKG mouse group were also detected.

CONCLUSION

Oral DSS administration alone elicited peripheral enthesitis in SKG mice with bacterial translocation accompanied by increased splenic Th1 and Th17 cell levels. Pre-administration of antibiotics ameliorated these DSS-induced SpA features. These findings suggest that intestinal bacterial leakage plays a pivotal role in SpA pathogenesis.

GW4064 Alters Gut Microbiota Composition and Counteracts Autism-Associated Behaviors in BTBR T+tf/J Mice

Autism spectrum disorder (ASD) is considered a heterogeneous neurodevelopmental disorder characterized by significant social, communication, and behavioral impairments. The gut microbiota is increasingly considered a promising therapeutic target in ASD. Farnesoid X receptor (FXR) has recently been shown to modulate the gut microbiota. We hypothesized that FXR agonist GW4064 could ameliorate behavioral deficits in an animal model for autism: BTBR T⁺Itpr3^tf/J (BTBR) mouse. As expected, administration of GW4064 rescued the sociability of BTBR mice in the three-chamber sociability test and male-female social reciprocal interaction test, while no effects were observed in C57BL/6J mice. We also found that GW4064 administration increased fecal microbial abundance and counteracted the common ASD phenotype of a high Firmicutes to Bacteroidetes ratio in BTBR mice. In addition, GW4064 administration reversed elevated Lactobacillus and decreased Allobaculum content in the fecal matter of BTBR animals. Our findings show that GW4064 administration alleviates social deficits in BTBR mice and modulates selective aspects of the composition of the gut microbiota, suggesting that GW4064 supplementation might prove a potential strategy for improving ASD symptoms.

Lactobacillus: Friend or Foe for Systemic Lupus Erythematosus?

The cause of Systemic Lupus Erythematosus (SLE) remains largely unknown, despite the fact that it is well understood that a complex interaction between genes and environment is required for disease development. Microbiota serve as activators and are essential to immune homeostasis. Lactobacillus is thought to be an environmental agent affecting the development of SLE. However, beneficial therapeutic and anti-inflammatory effects of Lactobacillus on SLE were also explored. The discovery of Lactobacillus involvement in SLE will shed light on how SLE develops, as well as finding microbiota-targeted biomarkers and novel therapies. In this review, we attempt to describe the two sides of Lactobacillus in the occurrence, development, treatment and prognosis of SLE. We also discuss the effect of different strains Lactobacillus on immune cells, murine lupus, and patients. Finally, we try to illustrate the potential immunological mechanisms of Lactobacillus on SLE and provide evidence for further microbiota-targeted therapies.

Dysbiosis of the Female Murine Gut Microbiome Exacerbates Neutrophil-Mediated Vascular Allograft Injury by Affecting Immunoregulation by Acetate

BACKGROUND

The gut microbiota affects immune responses that cause organ transplant rejection, but the mechanisms by which this occurs remain poorly understood.

METHODS

We have examined, in a murine model, how disruption of the gut microbiota with antibiotics early in life alters this microbial community later in life to affect immune responses that injure vascular allografts.

RESULTS

Analysis of 16S rRNA and whole genome sequencing of the gut microbiota demonstrated that early life disruption of this microbial community with antibiotics caused a reduction in taxa and enzymatic genes involved in the synthesis of acetate, an immunoregulatory metabolite in mice and humans. When allograft vascular injury was examined, early life disruption of the gut microbiota increased neutrophil accumulation and related medial injury of transplanted arteries. Normalizing the gut microbiota by co-housing and oral administration of acetate prevented neutrophil-mediated vascular allograft injury.

CONCLUSIONS

Dysbiosis of the gut microbiome that reduces its production of the immunoregulatory metabolite acetate exacerbates neutrophil-mediated allograft vascular injury.

Oral administration of Lactiplantibacillus plantarum NR16 isolated from Kimchi ameliorates murine allergic rhinitis

Allergic rhinitis (AR) is a type I hypersensitivity mediated by dominant T helper 2 (Th2) response over the Th1 response after re-exposure to a specific allergen. Currently, socio-economic cost evoked by AR is quickly increasing since the prevalence of AR is gradually increasing in all ages worldwide. Several probiotic Lactobacillus strains have been described with potential immunomodulatory effects against type I hypersensitivity such as AR. Thus, the aim of the present work was to characterize basic probiotic property and immunomodulatory role of newly isolated Lactobacillus strains from Kimchi, a traditional fermented Korean food, in allergic rhinitis. Among the identified strains, Lactiplantibacillus plantarum NR16 revealed to be a powerful Th1 inducer since immune cells co-cultured with NR16 produced the highest quantity of interferon-γ (IFN-γ) and interleukin-12 (IL-12) but secreted a low amount of IL-4 in vitro. Therefore, NR16 was selected for the following assays conducted with mice with birch pollen-induced allergic rhinitis. Oral administration of NR16 reduced airway hyperresponsiveness and leukocyte infiltration in lesions of mice. In conclusion, oral administration of NR16 may mitigate symptoms of allergic rhinitis by inducing Th1 immune response, which might rebalance Th2/Th1 ratio by decreasing Th2 cytokine production in specific lesions of mucosa.

Microbial Signatures in The Rodent Eyes With Retinal Dysfunction and Diabetic Retinopathy

Purpose

The gut microbiome has been linked to disease pathogenesis through their interaction in metabolic, endocrine, and immune functions. The goal of this study was to determine whether the gut and plasma microbiota could transfer microbes to the retina in type 1 diabetic mice with retinopathy.

Methods

We analyzed the fecal, plasma, whole globe, and retina microbiome in Akita mice and compared with age-matched wild-type (WT) mice using 16S rRNA sequencing and metatranscriptomic analysis. To eliminate the contribution of the ocular surface and plasma microbiome, mice were perfused with sterile saline solution, the whole globes were extracted, and the neural retina was removed under sterile conditions for retinal microbiome.

Results

Our microbiome analysis revealed that Akita mice demonstrated a distinct pattern of microbes within each source: feces, plasma, whole globes, and retina. WT mice and Akita mice experienced transient bacteremia in the plasma and retina. Bacteria were identified in the retina of the Akita mice, specifically Corynebacterium, Pseudomonas, Lactobacillus, Staphylococcus, Enterococcus, and Bacillus. Significantly increased levels of peptidoglycan (0.036 ± 0.001 vs. 0.023 ± 0.002; P < 0.002) and TLR2 (3.47 ± 0.15 vs. 1.99 ± 0.07; P < 0.0001) were observed in the retina of Akita mice compared to WT. Increased IBA⁺ cells in the retina, reduced a- and b-waves on electroretinography, and increased acellular capillary formation demonstrated the presence of retinopathy in the Akita cohort compared to WT mice.

Conclusions

Together, our findings suggest that transient bacteremia exists in the plasma and retina of both cohorts. The bacteria found in Akita mice are distinct from WT mice and may contribute to development of retinal inflammation and barrier dysfunction in retinopathy.

Abnormalities of the composition of the gut microbiota and short-chain fatty acids in mice after splenectomy

The brain–gut–microbiota axis is a complex multi-organ bidirectional signaling system between the brain and microbiota that participates in the host immune system. The spleen, as the largest immune organ in the body, has a key role in the brain–gut–microbiota axis. Here, we investigated whether splenectomy could affect depression-like phenotypes and the composition of the gut microbiota in adult mice. In behavioral tests, splenectomy did not cause depression-like behaviors in mice. Conversely, splenectomy led to significant alterations in the diversity of gut microbes compared with the findings in control (no surgery) and sham-operated mice. In an unweighted UniFrac distance analysis, the boxplots representing the splenectomy group were distant from those representing the other two groups. We found differences in abundance for several bacteria in the splenectomy group at the taxonomic level compared with the other two groups. Finally, splenectomy induced significant changes in lactic acid and n-butyric acid levels compared with those in the other groups. Interestingly, there were significant correlations between the counts of certain bacteria and lactic acid (or n-butyric acid) levels in all groups. These data suggest that splenectomy leads to an abnormal composition of the gut microbiota. It is likely that the spleen–gut–microbiota axis plays a crucial role in the composition of the gut microbiota by regulating immune homeostasis.

Abnormal composition of microbiota in the gut and skin of imiquimod-treated mice

Psoriasis is a chronic, inflammatory skin disease. Although the precise etiology of psoriasis remains unclear, gut-microbiota axis might play a role in the pathogenesis of the disease. Here we investigated whether the composition of microbiota in the intestine and skin is altered in the imiquimod (IMQ)-treated mouse model of psoriasis. Topical application of IMQ to back skin caused significant changes in the composition of microbiota in the intestine and skin of IMQ-treated mice compared to control mice. The LEfSe algorithm identified the species Staphylococcus lentus as potential skin microbial marker for IMQ group. Furthermore, there were correlations for several microbes between the intestine and skin, suggesting a role of skin-gut-microbiota in IMQ-treated mice. Levels of succinic acid and lactic acid in feces from IMQ-treated mice were significantly higher than control mice. Moreover, the predictive functional analysis of the microbiota in the intestine and skin showed that IMQ caused alterations in several KEGG pathways. In conclusion, the current data indicated that topical application with IMQ to skin alters the composition of the microbiota in the gut and skin of host. It is likely that skin-gut microbiota axis plays a role in pathogenesis of psoriasis.

Gut Dysbiosis Contributes to the Imbalance of Treg and Th17 Cells in Graves' Disease Patients by Propionic Acid

BACKGROUND

Graves' disease (GD) is a typical organ-specific autoimmune disease. Intestinal flora plays a pivotal role in immune homeostasis and autoimmune disease development. However, the association and mechanism between intestinal flora and GD remain elusive.

OBJECTIVE

To investigate the association and mechanism between intestinal flora and GD.

METHODS

We recruited 58 initially untreated GD patients and 63 healthy individuals in the study. The composition and metabolic characteristics of the intestinal flora in GD patients and the causal relationship between intestinal flora and GD pathogenesis were assessed using 16S rRNA gene sequencing, targeted/untargeted metabolomics, and fecal microbiota transplantation.

RESULTS

The composition, metabolism, and inter-relationships of the intestinal flora were also changed, particularly the significantly reduced short-chain fatty acid (SCFA)-producing bacteria and SCFAs. The YCH46 strain of Bacteroides fragilis could produce propionic acid and increase Treg cell numbers while decreasing Th17 cell numbers. Transplanting the intestinal flora of GD patients significantly increased GD incidence in the GD mouse model. Additionally, there were 3 intestinal bacteria genera (Bacteroides, Alistipes, Prevotella) could distinguish GD patients from healthy individuals with 85% accuracy.

CONCLUSIONS

Gut dysbiosis contributes to a Treg/Th17 imbalance through the pathway regulated by propionic acid and promotes the occurrence of GD, together with other pathogenic factors. Bacteroides, Alistipes, and Prevotella have great potential to serve as adjunct markers for GD diagnosis. This study provided valuable clues for improving immune dysfunction of GD patients using B. fragilis and illuminated the prospects of microecological therapy for GD as an adjunct treatment.