Alterations and Mechanism of Gut Microbiota in Graves' Disease and Hashimoto's Thyroiditis

The conspiring role of gut microbiota as primer of autoimmune thyroid diseases: A scoping focus

The thyroid gland is the body's largest single organ specialized for endocrine hormone production, and still unraveled mechanisms regulate its interaction between the hypothalamic-pituitary-thyroid axis and composition of the gut microbiota: in particular, a disrupted integrity of the intestinal barrier, causing dysbiosis and increasing detrimental substances or reducing beneficial metabolites, such as short-chain fatty acids (SCFAs) with proinflammatory effects, may be crucial for the induction of an autoimmune thyroid disease. More specifically, Lactobacilli and Bifidobacteria have a role in this partnership through a "molecular mimicry" mechanism, as their protein sequences share structural similarity with thyroid peroxidase and thyroglobulin. Lactobacilli can also increase T helper 17 cells, modifying the number of colonic regulatory T cells, largely implicated in the maintenance of immunological tolerance at the gut barrier. Additionally, Blautia and Anaerostipes work beneficially with butyric acid, one of the SCFAs, promoting antimicrobial peptide synthesis from the intestinal cells and bolstering the innate immune system's ability to struggle against pathogens, which can also influence thyroid hormone levels by regulating iodine uptake and metabolism. This review aims to summarize the current knowledge about the contribution of gut microbiota changes in triggering immune abnormalities leading to autoimmune thyroid diseases.

Unveiling shifts in cervical microbiota composition among Colombian women in the presence of Trichomonas vaginalis: a longitudinal study

Trichomonas vaginalis is a flagellated protozoan affecting human reproductive health. Although bacterial coinfections have been associated with T. vaginalis infection outcomes, pertinent data are scarce. This study was aimed at assessing vaginal bacterial community changes regarding T. vaginalis outcomes (infection, clearance, persistence) during patients' follow-up visits. This was a 1-year follow-up study involving Colombian women who provided two cytological scrapings from the cervix (one at baseline and another at follow-up), having an average 12 ± 1 month follow-up interval. T. vaginalis was detected by conventional PCR (Tvk3/7 and BTU9/2 primers). The Illumina Novaseq PE250-platform was used for assessing microbiota composition. This study involved 66 women (132 samples); 68.2% (n = 45) tested negative for T. vaginalis at baseline while 31.8% (n = 21) were initially diagnosed with T. vaginalis infection (99,304 amplicon sequence variants identified/categorised into 62 phyla and 1908 genera). Women who cleared T. vaginalis (n = 10) displayed increased microbial richness, while those having persistence (n = 11) had higher microbial diversity. Significant changes were observed regarding genus relative abundance: Lactobacillus abundance increased in the clearance group (p = 0.002), Prevotella in the persistence group (p = 0.045) and Gardnerella, Megasphaera and Sneathia in the group having acquired T. vaginalis infection (p = 0.045). Regarding relative abundance, logistic regression analysis revealed a positive trend concerning Sneathia increase (adjusted OR 2.23) and reduced Lactobacillus abundance (adjusted OR 0.39) in women with T. vaginalis persistence. DESeq analysis revealed a substantial decrease in the Ornithinimicrobium genus among women without infection during follow-up, while Ruminococcus increased in women having various T. vaginalis outcomes. The results suggested that specific bacterial genera present during T. vaginalis infection may influence its clearance, having potential implications for improving diagnostic and therapeutic strategies for enhancing women's reproductive health.

Elimination of oral foci of infection might lead to clinical improvement of Graves' orbitopathy

PURPOSE

Graves' disease (GD) and Graves' orbitopathy (GO) are multifactorial disorders with links to the gut microbiome and autoimmunity. It is observed that patients with GD exhibit altered gut microbiome diversity. However, little is known about the role of oral microbiota in GD and GO. This study aims to investigate the impact of oral health and oral sanitation on the clinical course of GO in patients disqualified from glucocorticoid treatment due to oral infections.

METHODS

We reviewed 188 admissions of 127 patients with GO, hospitalized in a tertiary university hospital. Clinical, biochemical, imaging, ophthalmological, and oral health assessment data from each admission were analyzed. Patients excluded from the glucocorticoids (GCs) therapy due to oral foci of infection had the clinical activity score (CAS) reassessed after three months, and they were divided into two groups: with and without improvement.

RESULTS

Finishing dental treatment in the meantime was the only factor significantly correlated with improvement in these patients (p = 0.041). The secondary finding was that anti-thyroid peroxidase antibodies titer was significantly higher in the group with oral foci of infection considered as a contraindication for GCs (medians 28.50 vs 128.00; p = 0.026), and those patients were more likely to smoke than the group without oral issues (p = 0.024).

CONCLUSIONS

The results of our study suggest that monitoring and treating oral diseases may be pertinent in patients with GO and might serve as a supportive treatment strategy for managing the condition.

KEY MESSAGES

What is known: There is a recognized link between gut dysbiosis and the autoimmune processes in Graves' Disease (GD) and Graves' Orbitopathy (GO).

WHAT IS NEW

Elevated levels of TPOAb have been observed in patients with GO who also have oral foci of infection. Dental treatment has been shown to lead to significant clinical improvements in patients with GO. Maintaining oral hygiene might serve as a supportive treatment strategy for managing GO.

Recent advances in gut microbiota and thyroid disease: pathogenesis and therapeutics in autoimmune, neoplastic, and nodular conditions

This review synthesizes key findings from the past five years of experimental literature, elucidating the gut microbiome's significant influence on the pathogenesis of thyroid diseases. A pronounced shift in the gut microbiota composition has been consistently observed, with a significant reduction in bacteria such as Bifidobacterium, Bacillaceae, Megamonas, and Clostridium, and a notable increase in bacteria, including Bacteroides, Proteobacteria, Actinobacteria, Desulfobacterota, and Klebsiella. These alterations are implicated in the development and progression of thyroid diseases by impacting metabolic pathways including bile acid and cytokine production, including a decrease in short-chain fatty acids (SCFAs) that are crucial for immune regulation and thyroid hormone homeostasis. The review also highlights the therapeutic implications of probiotics in managing thyroid conditions. Evidence suggests that probiotic adjunct therapy can modulate the gut microbiota, leading to improvements in thyroid function and patient outcomes. The use of specific probiotic strains, such as Lactiplantibacillus plantarum 299v and Bifidobacterium longum, has demonstrated potential in enhancing the effects of traditional treatments and possibly restoring a balanced gut microbiota. Notably, fecal microbiota transplantation (FMT) has emerged as a promising intervention in Graves' Disease (GD), demonstrating the potential to recalibrate the gut microbiota, thereby influencing neurotransmitters and trace elements via the gut-brain and gut-thyroid axes. The integration of microbiome-based therapies with traditional treatments is anticipated to usher in a new era of personalized thyroid disease management, offering a more nuanced approach to patient care. By integrating this body of work, the review offers an innovative perspective on the gut microbiome's broad impact on thyroid diseases and the therapeutic applications of probiotics.

Association between small intestine bacterial overgrowth and psychiatric disorders

Small intestinal bacterial overgrowth (SIBO) is a gastrointestinal condition characterized by abnormal colonization of bacteria in the small intestine, leading to overgrowth and alteration, which is linked to gastrointestinal issues, potentially affecting neurological and mental health. Despite existing research, we still do not understand how SIBO affects tryptophan metabolism and psychiatric diseases. We investigated the literature for connections between SIBO, tryptophan metabolism disruptions, and psychiatric disorders like autism, schizophrenia, Alzheimer's, and Parkinson's diseases. We also explored the interaction between thyroid disorders and their influence on SIBO and psychiatric illnesses. PubMed and Google Scholar databases were searched using keywords and phrases, individual and in combinations, like "SIBO," "gut microbiota," "neurologic disorders," "mental disorders," "tryptophan," "dopamine," and "thyroid disease." We focused on original research and review papers that presented empirical studies conducted on animal models and human subjects published in English between February 1992 to February 2023. The initial 2 634 534 records were preliminary screened based on title and abstract and then subjected to full-text review to exclude publications with insufficient data on SIBO, lack of a psychiatric disorder component, or methodological limitations compromising the integrity of the findings. The analysis highlights the significance of the association between psychiatric disorders and SIBO, emphasizing the role of gut-microbial diversity in mental health. We advocate for more detailed studies, including longitudinal research, to clarify the causal relationships between SIBO, gut dysbiosis, and psychiatric disorders and for an integrated approach while treating complex psychiatric conditions.

Unveiling the Role of Gut Microbiota and Metabolites in Autoimmune Thyroid Diseases: Emerging Perspectives

Autoimmune thyroid diseases (AITDs) are among the most prevalent organ-specific autoimmune disorders, with thyroid hormones playing a pivotal role in the gastrointestinal system's structure and function. Emerging evidence suggests a link between AITDs and the gut microbiome, which is a diverse community of organisms that are essential for digestion, absorption, intestinal homeostasis, and immune defense. Recent studies using 16S rRNA and metagenomic sequencing of fecal samples from AITD patients have revealed a significant correlation between a gut microbiota imbalance and the severity of AITDs. Progress in animal models of autoimmune diseases has shown that intervention in the gut microbiota can significantly alter the disease severity. The gut microbiota influences T cell subgroup differentiation and modulates the pathological immune response to AITDs through mechanisms involving short-chain fatty acids (SCFAs), lipopolysaccharides (LPSs), and mucosal immunity. Conversely, thyroid hormones also influence gut function and microbiota composition. Thus, there is a bidirectional relationship between the thyroid and the gut ecosystem. This review explores the pathogenic mechanisms of the gut microbiota and its metabolites in AITDs, characterizes the gut microbiota in Graves' disease (GD) and Hashimoto's thyroiditis (HT), and examines the interactions between the gut microbiota, thyroid hormones, T cell differentiation, and trace elements. The review aims to enhance understanding of the gut microbiota-thyroid axis and proposes novel approaches to mitigate AITD severity through gut microbiota modulation.

Fecal microbiota transplantation in autoimmune diseases - An extensive paper on a pathogenetic therapy

The role of infections in the pathogenesis of autoimmune diseases has long been recognized and reported. In addition to infectious agents, the internal composition of the "friendly" living bacteria, (microbiome) and its correlation to immune balance and dysregulation have drawn the attention of researchers for decades. Nevertheless, only recently, scientific papers regarding the potential role of transferring microbiome from healthy donor subjects to patients with autoimmune diseases has been proposed. Fecal microbiota transplantation or FMT, carries the logic of transferring microorganisms responsible for immune balance from healthy donors to individuals with immune dysregulation or more accurately for our paper, autoimmune diseases. Viewing the microbiome as a pathogenetic player allows us to consider FMT as a pathogenetic-based treatment. Promising results alongside improved outcomes have been demonstrated in patients with different autoimmune diseases following FMT. Therefore, in our current extensive review, we aimed to highlight the implication of FMT in various autoimmune diseases, such as inflammatory bowel disease, autoimmune thyroid and liver diseases, systemic lupus erythematosus, and type 1 diabetes mellitus, among others. Presenting all the aspects of FMT in more than 12 autoimmune diseases in one paper, to the best of our knowledge, is the first time presented in medical literature. Viewing FMT as such could contribute to better understanding and newer application of the model in the therapy of autoimmune diseases, indeed.

Exploring the Role of Gut Microbiota in Patients with Alopecia Areata

Imbalances in gut microbiota reportedly contribute to the development of autoimmune diseases, but the association between the etiopathogenesis of alopecia areata (AA) and gut microbial dysbiosis remains unclear. This cross-sectional study was conducted to identify and compare the composition of the gut microbiome in patients affected by AA and those in a healthy control (HC) group, and to investigate possible bacterial biomarkers for the disease. Fecal samples were collected from 19 AA patients and 20 HCs to analyze the relationship with fecal bacteria. The three major genera constituting the gut microbiome of AA patients were Bacteroides, Blautia, and Faecalibacterium. The alpha diversity of the AA group was not statistically significant different from that of the HC group. However, bacterial community composition in the AA group was significantly different from that of HC group according to Jensen-Shannon dissimilarities. In patients with AA, we found an enriched presence of the genera Blautia and Eubacterium_g5 compared to the HC group (p < 0.05), whereas Bacteroides were less prevalent (p < 0.05). The gut microbiota of AA patients was distinct from those of the HC group. Our findings suggest a possible involvement of gut microbiota in in the as-yet-undefined pathogenesis of AA.

Alteration in gut microbiota is associated with immune imbalance in Graves' disease

Background

Graves' disease (GD), characterized by immune aberration, is associated with gut dysbiosis. Despite the growing interest, substantial evidence detailing the precise impact of gut microbiota on GD's autoimmune processes remains exceedingly rare.

Objective

This study was designed to investigate the influence of gut microbiota on immune dysregulation in GD.

Methods

It encompassed 52 GD patients and 45 healthy controls (HCs), employing flow cytometry and enzyme-linked immunosorbent assay to examine lymphocyte and cytokine profiles, alongside lipopolysaccharide (LPS) levels. Gut microbiota profiles and metabolic features were assessed using 16S rRNA gene sequencing and targeted metabolomics.

Results

Our observations revealed a disturbed B-cell distribution and elevated LPS and pro-inflammatory cytokines in GD patients compared to HCs. Significant differences in gut microbiota composition and a marked deficit in short-chain fatty acid (SCFA)-producing bacteria, including ASV263(Bacteroides), ASV1451(Dialister), and ASV503(Coprococcus), were observed in GD patients. These specific bacteria and SCFAs showed correlations with thyroid autoantibodies, B-cell subsets, and cytokine levels. In vitro studies further showed that LPS notably caused B-cell subsets imbalance, reducing conventional memory B cells while increasing naïve B cells. Additionally, acetate combined with propionate and butyrate showcased immunoregulatory functions, diminishing cytokine production in LPS-stimulated cells.

Conclusion

Overall, our results highlight the role of gut dysbiosis in contributing to immune dysregulation in GD by affecting lymphocyte status and cytokine production.

The impact of gut microbiota on autoimmune thyroiditis and relationship with pregnancy outcomes: a review

Autoimmune thyroiditis (AITD) is a T-cell-mediated, organ- specific autoimmune disease caused by interactions between genetic and environmental factors. Patients with AITD show thyroid lymphocyte infiltration and an increase in the titer of thyroid autoimmune antibodies, thereby altering the integrity of thyroid follicle epithelial cells and dysregulating their metabolism and immune function, leading to a decrease in multi-tissue metabolic activity. Research has shown that patients with AITD have a significantly higher risk of adverse pregnancy outcomes, such as infertility and miscarriage. Levothyroxine(LT4) treatment can improve the pregnancy outcomes of normal pregnant women with thyroid peroxidase antibodies(TPOAb) positivity, but it is not effective for invitro fertilization embryo transfer (IVF-ET) in women with normal thyroid function and positive TPOAb. Other factors may also influence pregnancy outcomes of patients with AITD. Recent studies have revealed that the gut microbiota participates in the occurrence and development of AITD by influencing the gut-thyroid axis. The bacterial abundance and diversity of patients with Hashimoto thyroiditis (HT) were significantly reduced, and the relative abundances of Bacteroides, fecal Bacillus, Prevotella, and Lactobacillus also decreased. The confirmation of whether adjusting the composition of the gut microbiota can improve pregnancy outcomes in patients with AITD is still pending. This article reviews the characteristics of the gut microbiota in patients with AITD and the current research on its impact in pregnancy.

Dynamic alterations of locomotor activity and the microbiota in zebrafish larvae with low concentrations of lead exposure

Lead (Pb) is a ubiquitous heavy metal associated with developmental and behavioral disorders. The establishment of pioneer microbiota overlaps with the development of the brain during early life, and Pb-induced developmental neurotoxicity may be partially caused by early-life microbiota dysbiosis. This study investigated the locomotor activity and the microbiota in developing zebrafish at multiple developmental time points (five days post fertilization [5 dpf], 6 dpf, and 7 dpf) under exposure to low concentrations of lead (0.05 mg/L). Time-dependent reductions in the number of activities and the average movement distance of larvae compared to the control were observed following Pb exposure. Furthermore, Pb exposure significantly altered the composition of the gut microbiota of zebrafish larvae. At the phylum level, the abundance of Proteobacteria decreased from 5 to 7 dpf, while that of Actinobacteria increased in the control groups. At the class level, the proportion of Alphaproteobacteria decreased, while that of Actinobacteria increased in the control groups. Notably, all showed the opposite trend in Pb groups. A correlation analysis between indices of locomotor activity and microbial communities revealed genus-level features that were clearly linked to the neurobehavioral performance of zebrafish. Seven genera were significantly correlated with the two performance indicators of the locomotion analysis, namely Rhodococcus, Deinococcus, Bacillus, Bosea, Bradyrhizobium, Staphylococcus, and Rhizobium. Rhizobium was dominant in zebrafish and increased in the Pb groups in a time-dependent manner. In addition, the expression levels of bdnf, trkb1, trkb2, and p75ntr changed in zebrafish from 5 to 7 dpf under Pb exposure. Collectively, these results suggest that Pb-induced neurotoxicity could potentially be treated by targeting the gut microbiota.

Mapping the path towards novel treatment strategies: a bibliometric analysis of Hashimoto's thyroiditis research from 1990 to 2023

Background

Hashimoto's thyroiditis (HT), a common form of thyroid autoimmunity, is strongly associated with deteriorating clinical status and impaired quality of life. The escalating global prevalence, coupled with the complexity of disease mechanisms, necessitates a comprehensive, bibliometric analysis to elucidate the trajectory, hotspots, and future trends in HT research.

Objective

This study aims to illuminate the development, hotspots, and future directions in HT research through systematic analysis of publications, institutions, authors, journals, references, and keywords. Particular emphasis is placed on novel treatment strategies for HT and its complications, highlighting the potential role of genetic profiling and immunomodulatory therapies.

Methods

We retrieved 8,726 relevant documents from the Web of Science Core Collection database spanning from 1 January 1990 to 7 March 2023. Following the selection of document type, 7,624 articles were included for bibliometric analysis using CiteSpace, VOSviewer, and R software.

Results

The temporal evolution of HT research is categorized into three distinct phases: exploration (1990-1999), rapid development (1999-2000), and steady growth (2000-present). Notably, the United States, China, Italy, and Japan collectively contributed over half (54.77%) of global publications. Among the top 10 research institutions, four were from Italy (4/10), followed by China (2/10) and the United States (2/10). Recent hotspots, such as the roles of gut microbiota, genetic profiling, and nutritional factors in HT management, the diagnostic dilemmas between HT and Grave's disease, as well as the challenges in managing HT complicated by papillary thyroid carcinoma and type 1 diabetes mellitus, are discussed.

Conclusion

Although North America and Europe have a considerable academic impact, institutions from emerging countries like China are demonstrating promising potential in HT research. Future studies are anticipated to delve deeper into the differential diagnosis of HT and Grave's disease, the intricate relationship between gut microbiota and HT pathogenesis, clinical management of HT with papillary thyroid carcinoma or type 1 diabetes, and the beneficial effects of dietary modifications and micronutrients supplementation in HT. Furthermore, the advent of genetic profiling and advanced immunotherapies for managing HT offers promising avenues for future research.

Oral Microbiota Signatures in the Pathogenesis of Euthyroid Hashimoto’s Thyroiditis

One of the most prevalent autoimmune illnesses in the world is Hashimoto’s thyroiditis, whose pathogenesis is still unknown. The gut–thyroid axis is frequently examined, and although oral health affects thyroid functions, there are limited data on how oral microbiota is linked to Hashimoto’s thyroiditis. The study aims to identify the oral microbiota from saliva samples taken from treated (with levothyroxine) and untreated female euthyroid Hashimoto’s thyroiditis patients as well as healthy controls who were age- and sex-matched to compare the oral microbiota across the groups and to contribute preliminary data to the literature. This study was designed as a single-center cross-sectional observational study. Sixty (60) female patients with euthyroid Hashimoto’s thyroiditis (HT) and eighteen (18) age- and gender-matched healthy controls were included in this study. Unstimulated saliva samples were collected. After DNA isolation, sequencing was performed by targeting the V3-V4 gene regions of the 16S rRNA on the MiSeq instrument. R scripts and SPSS were used for bioinformatic and statistical analysis. No significant differences were found in the diversity indices. However, Patescibacteria phylum showed a significantly higher abundance (3.59 vs. 1.12; p = 0.022) in the oral microbiota of HT patients compared to HC. In the oral microbiota, the euthyroid HT group had approximately 7, 9, and 10-fold higher levels of the Gemella, Enterococcus, and Bacillus genera levels than healthy controls, respectively. In conclusion, the results of our study demonstrated that Hashimoto’s thyroiditis causes changes in the oral microbiota, whereas the medicine used to treat the condition had no such effects. Therefore, revealing the core oral microbiota and long-term follow-up of the HT process by conducting extensive and multicenter studies might provide some important data for understanding the pathogenesis of the disease.

Molecular Mechanisms in Autoimmune Thyroid Disease

The most common cause of acquired thyroid dysfunction is autoimmune thyroid disease, which is an organ-specific autoimmune disease with two presentation phenotypes: hyperthyroidism (Graves-Basedow disease) and hypothyroidism (Hashimoto's thyroiditis). Hashimoto's thyroiditis is distinguished by the presence of autoantibodies against thyroid peroxidase and thyroglobulin. Meanwhile, autoantibodies against the TSH receptor have been found in Graves-Basedow disease. Numerous susceptibility genes, as well as epigenetic and environmental factors, contribute to the pathogenesis of both diseases. This review summarizes the most common genetic, epigenetic, and environmental mechanisms involved in autoimmune thyroid disease.

Morphological and genomic characteristics of two novel actinomycetes, Ornithinimicrobium sufpigmenti sp. nov. and Ornithinimicrobium faecis sp. nov. isolated from bat faeces (Rousettus leschenaultia and Taphozous perforates)

Four Gram-staining-positive, aerobic, non-motile, circle-shaped bacteria were isolated from the faeces of bats (Rousettus leschenaultia and Taphozous perforates) collected from Guangxi autonomous region (E106°49'20″, N22°20'54″) and Yunnan province (E102°04'39″, N25°09'10″) of South China. Strains HY006^T and HY008 shared highly 16S rRNA gene sequence similarity to those of Ornithinimicrobium pratense W204^T (99.3%) and O. flavum CPCC 203535^T (97.3%), while the strains HY1745 and HY1793^T were closest to the type strains O. ciconiae H23M54^T (98.7%), O. cavernae CFH 30183^T (98.3%), and O. murale 01-Gi-040^T (98.1%). Furthermore, when compared to the other members of the genus Ornithinimicrobium, the digital DNA-DNA hybridization and average nucleotide identity values of the four novel strains were within the ranges of 19.6-33.7% and 70.6-87.4%, respectively, both of which were below the respective recommended cutoff values of 70.0% and 95-96%. Significantly, strain HY006^T was resistant to chloramphenicol and linezolid whereas strain HY1793^T was resistant to erythromycin, clindamycin (intermediately), and levofloxacin (intermediately). The main cellular fatty acids (>20.0%) of our isolates were iso-C_15:0 and iso-C_16:0. Strains HY006^T and HY1793^T contained ornithine as the diagnostic diamino acid, also along with the alanine, glycine and glutamic acid in their cell wall. Based on phylogenetic, chemotaxonomic and phenotypic analyses, these four strains could be classified as two novel species of the genus Ornithinimicrobium, for which the names Ornithinimicrobium sufpigmenti sp. nov. and Ornithinimicrobium faecis sp. nov. are proposed. The type strains are HY006^T (=CGMCC 1.16565^T =JCM 33397^T) and HY1793^T (=CGMCC 1.19143^T =JCM 34881^T), respectively.

Gut Dysbiosis and Fecal Microbiota Transplantation in Autoimmune Diseases

Gut microbiota dysbiosis has recently been reported in a number of clinical states, including neurological, psychiatric, cardiovascular, metabolic and autoimmune disorders. Yet, it is not completely understood how colonizing microorganisms are implicated in their pathophysiology and molecular pathways. There are a number of suggested mechanisms of how gut microbiota dysbiosis triggers or sustains extraintestinal diseases; however, none of these have been widely accepted as part of the disease pathogenesis. Recent studies have proposed that gut microbiota and its metabolites could play a pivotal role in the modulation of immune system responses and the development of autoimmunity in diseases such as rheumatoid arthritis, multiple sclerosis or type 1 diabetes. Fecal microbiota transplantation (FMT) is a valuable tool for uncovering the role of gut microbiota in the pathological processes. This review aims to summarize the current knowledge about gut microbiota dysbiosis and the potential of FMT in studying the pathogeneses and therapies of autoimmune diseases. Herein, we discuss the extraintestinal autoimmune pathologies with at least one published or ongoing FMT study in human or animal models.