Molecular estimation of alteration in intestinal microbial composition in Hashimoto’s thyroiditis patients

The epithelial barrier theory and its associated diseases

The prevalence of many chronic noncommunicable diseases has been steadily rising over the past six decades. During this time, over 350,000 new chemical substances have been introduced to the lives of humans. In recent years, the epithelial barrier theory came to light explaining the growing prevalence and exacerbations of these diseases worldwide. It attributes their onset to a functionally impaired epithelial barrier triggered by the toxicity of the exposed substances, associated with microbial dysbiosis, immune system activation, and inflammation. Diseases encompassed by the epithelial barrier theory share common features such as an increased prevalence after the 1960s or 2000s that cannot (solely) be accounted for by the emergence of improved diagnostic methods. Other common traits include epithelial barrier defects, microbial dysbiosis with loss of commensals and colonization of opportunistic pathogens, and circulating inflammatory cells and cytokines. In addition, practically unrelated diseases that fulfill these criteria have started to emerge as multimorbidities during the last decades. Here, we provide a comprehensive overview of diseases encompassed by the epithelial barrier theory and discuss evidence and similarities for their epidemiology, genetic susceptibility, epithelial barrier dysfunction, microbial dysbiosis, and tissue inflammation.

Integrative analysis of gut microbiome and host transcriptome reveal novel molecular signatures in Hashimoto's thyroiditis

BACKGROUND

Hashimoto's thyroiditis (HT) is an autoimmune disorder with unclear molecular mechanisms. While current diagnosis is well-established, understanding of the gut-thyroid axis in HT remains limited. This study aimed to uncover novel molecular signatures in HT by integrating gut metagenome and host transcriptome data (miRNA/mRNA), potentially elucidating disease pathogenesis and identifying new therapeutic targets.

METHODS

We recruited 31 early HT patients and 30 healthy controls in a two-stage study (discovery and validation). Blood and fecal samples underwent RNA and metagenomic sequencing, respectively. Integrative analysis included differential expression, weighted correlation network, correlation and random forest analyses. Regression models and ROC curve analysis were used to evaluate the significance of identified molecular signatures in HT.

RESULTS

Integrative analysis revealed subtle changes in gut microbiota diversity and composition in early HT, increased abundance of Bacillota_A and Spirochaetota at the phylum level, and significant differences in 24 genera and 67 species. Ecological network analysis indicated an imbalance in the gut microbiota with reduced inhibitory interactions against pathogenic genera in HT. Functional analysis showed changes in infection- and immune-related pathways. Three characteristic species (Salaquimonas_sp002400845, Clostridium_AI_sp002297865, and Enterocloster_citroniae) were identified as most relevant to HT. Analysis of miRNA and mRNA expression profiles uncovered pathways related to immune response, inflammation, infection, metabolism, proliferation, and thyroid cancer in HT. Based on correlations with HT and interactions between them, six characteristic RNAs (hsa-miR-548aq-3p, hsa-miR-374a-5p, GADD45A, IRS2, SMAD6, WWTR1) were identified. Furthermore, our study uncovered significant gut microbiota-host transcriptome interactions in HT, revealing enrichment in metabolic, immune, and cancer-related pathways, particularly with strong associations among those 9 key molecular signatures. The validation stage confirmed improved HT classification accuracy by combining these signatures (AUC = 0.95, ACC = 0.85), suggesting their potential significance in understanding HT pathogenesis.

CONCLUSION

Our study reveals novel molecular signatures linking gut microbiome and host transcriptome in HT, providing new insights into the disease pathogenesis. These findings not only enhance our understanding of the gut-thyroid axis but also suggest potential new directions for therapeutic interventions in HT.

The Gut Microbiota and Its Metabolites and Their Association with the Risk of Autoimmune Thyroid Disease: A Mendelian Randomization Study

Objectives: Observational research shows associations of the gut microbiota and its metabolites with autoimmune thyroid disease (AITD), but the causality is undetermined. Methods: Two-sample Mendelian randomization (MR) was employed to analyze the association of the gut microbiota and its metabolites with AITD. A total of 119 gut microbiotas and nine fecal/circulating metabolites were the exposures. AITD, Graves' disease (GD), and Hashimoto's thyroiditis (HT) were the outcomes. Inverse-variance weighting (IVW) was primarily used to assess causality; Cochran's Q was used to assess heterogeneity. Sensitivity analyses (weighted median, MRPRESSO regression, MRPRESSO intercept, MRPRESSO global, Steiger filtering, leave-one-out) were conducted to assess causal estimate robustness. Multivariable MR (MVMR) was used to estimate the effects of body mass index (BMI) and alcohol consumption frequency on causality. Results: The outcomes were potentially causally associated with 22 gut microbiotas and three metabolites. After multiple-test correction, 3-indoleglyoxylic acid retained significant causality with AITD (IVW: odds ratio [OR] = 1.09, 95% confidence interval [CI] = 1.05-1.14, p = 2.43 × 10-5, FDR = 0.009). The sensitivity analyses were confirmatory (weighted median: OR = 1.06, 95% CI = 1.01-1.12, p = 0.025; MRPRESSO: OR = 1.09, 95% CI = 1.15-1.14, p = 0.001). MVMR revealed no confounding effects on this association (BMI: OR = 1.21, 95% CI =1.08-1.35, p = 0.001; drinks/week: OR = 1.22, 95% CI = 1.04-1.43, p = 0.014). Conclusions: MR revealed no significant causal effects of the gut microbiota on the outcomes. However, MR revealed the causal effects of 3-indoleglyoxylic acid on the risk of AITD.

Causal relationship between gut microbiota and thyroid nodules: a bidirectional two-sample Mendelian randomization study

Objective

Emerging evidence suggests alterations in gut microbiota (GM) composition following thyroid nodules (TNs) development, yet the causal relationship remains unclear. Utilizing Mendelian Randomization (MR), this study aims to elucidate the causal dynamics between GM and TNs.

Methods

Employing summary statistics from the MiBioGen consortium (n=18,340) and FinnGen consortium (1,634 TNs cases, 263,704 controls), we conducted univariable and multivariable MR analyses to explore the GM-TNs association. Techniques including inverse variance weighted, MR-Egger regression, weighted median, and MR-PRESSO were utilized for causal inference. Instrumental variable heterogeneity was assessed through Cochran's Q statistic and leave-one-out analysis. Reverse MR was applied for taxa showing significant forward MR associations, with multivariate adjustments for confounders.

Results

Our findings suggest that certain microbiota, identified as Ruminococcaceae_NK4A214_group (OR, 1.89; 95%CI, 0.47-7.64; p = 0.040), Senegalimassilia (OR, 1.72; 95%CI, 1.03-2.87; p =0.037), Lachnospiraceae (OR,0.64; 95%CI,0.41-0.99; p =0.045), exhibit a protective influence against TNs' development, indicated by negative causal associations. In contrast, microbiota categorized as Desulfovibrionales (OR, 0.63; 95%CI, 0.41-0.95; p =0.028), Prevotella_7 (OR, 0.79; 95%CI, 0.63-1.00; p =0.049), Faecalibacterium (OR, 0.66; 95%CI, 0.44-1.00; p =0.050), Desulfovibrionaceae (OR, 0.55; 95%CI, 0.35-0.86; p =0.008), Deltaproteobacteria (OR, 0.65; 95%CI, 0.43-0.97; p =0.036) are have a positive correlation with with TNs, suggesting they may serve as risk factors. Reverse MR analyses did not establish significant causal links. After comprehensive adjustment for confounders, taxa Desulfovibrionales (Order), Desulfovibrionaceae (Family), Deltaproteobacteria (Class) remain implicated as potential contributors to TNs' risk.

Discussion

This study substantiates a significant causal link between GM composition and TNs development, underscoring the thyroid-gut axis's relevance. The findings advocate for the integration of GM profiles in TNs' prevention and management, offering a foundation for future research in this domain.

The relationship between the gut microbiota and thyroid disorders

Disorders of the thyroid gland are common, more prevalent in women than in men, and range from inflammatory to neoplastic lesions. Autoimmune thyroid diseases (AITD) affect 2-5% of the population, while thyroid cancer is the most frequent endocrine malignancy. Treatment for AITD is still restricted to management rather than prevention or cure. Progress has been made in identifying genetic variants that predispose to AITD and thyroid cancer, but the increasing prevalence of all thyroid disorders indicates that factors other than genes are involved. The gut microbiota, which begins to develop before birth, is highly sensitive to diet and the environment, providing a potential mechanism for non-communicable diseases to become communicable. Its functions extend beyond maintenance of gut integrity: the gut microbiota regulates the immune system, contributes to thyroid hormone metabolism and can generate or catabolize carcinogens, all of which are relevant to AITD and thyroid cancer. Observational and interventional studies in animal models support a role for the gut microbiota in AITD, which has been confirmed in some reports from human cohorts, although considerable geographic variation is apparent. Reports of a role for the microbiota in thyroid cancer are more limited, but evidence supports a relationship between gut dysbiosis and thyroid cancer.

Gut microbial β-glucuronidases influence endobiotic homeostasis and are modulated by diverse therapeutics

Hormones and neurotransmitters are essential to homeostasis, and their disruptions are connected to diseases ranging from cancer to anxiety. The differential reactivation of endobiotic glucuronides by gut microbial β-glucuronidase (GUS) enzymes may influence interindividual differences in the onset and treatment of disease. Using multi-omic, in vitro, and in vivo approaches, we show that germ-free mice have reduced levels of active endobiotics and that distinct gut microbial Loop 1 and FMN GUS enzymes drive hormone and neurotransmitter reactivation. We demonstrate that a range of FDA-approved drugs prevent this reactivation by intercepting the catalytic cycle of the enzymes in a conserved fashion. Finally, we find that inhibiting GUS in conventional mice reduces free serotonin and increases its inactive glucuronide in the serum and intestines. Our results illuminate the indispensability of gut microbial enzymes in sustaining endobiotic homeostasis and indicate that therapeutic disruptions of this metabolism promote interindividual response variabilities.

Vitamin D: An Essential Nutrient in the Dual Relationship between Autoimmune Thyroid Diseases and Celiac Disease-A Comprehensive Review

Autoimmune thyroid diseases (AITD) are among the most frequent autoimmune disorders, with a multifactorial etiology in which both genetic and environmental determinants are probably involved. Celiac disease (CeD) also represents a public concern, given its increasing prevalence due to the recent improvement of screening programs, leading to the detection of silent subtypes. The two conditions may be closely associated due to common risk factors, including genetic setting, changes in the composition and diversity of the gut microbiota, and deficiency of nutrients like vitamin D. This comprehensive review discussed the current evidence on the pivotal role of vitamin D in modulating both gut microbiota dysbiosis and immune system dysfunction, shedding light on the possible relevance of an adequate intake of this nutrient in the primary prevention of AITD and CeD. While future technology-based strategies for proper vitamin D supplementation could be attractive in the context of personalized medicine, several issues remain to be defined, including standardized assays for vitamin D determination, timely recommendations on vitamin D intake for immune system functioning, and longitudinal studies and randomized controlled trials to definitely establish a causal relationship between serum vitamin D levels and the onset of AITD and CeD.

The gut-brain-axis: A positive relationship between gut microbial dysbiosis and glioblastoma brain tumour

The glioblastoma brain tumour (GBM) stands out as the most aggressive and resistant-to-treatment malignancy. Nevertheless, the gut-brain connection plays a pivotal role in influencing the growth and activation of the central nervous system. In this particular investigation, we aimed to assess and characterize the gut microbial ecosystem in GBM patients, both quantitatively and qualitatively. We collected faecal samples from 15 healthy volunteers and 25 GBM patients. To delve into the microbial content, we employed PCR-DGGE, targeting the V3 region of the 16S rRNA gene, and conducted qPCR to measure the levels of crucial intestinal bacteria. For a more in-depth analysis, high-throughput sequencing was performed on a selection of 20 random faecal samples (10 from healthy individuals and 10 from GBM patients), targeting the V3+V4 region of the 16S rRNA gene. Our findings from examining the richness and diversity of the gut microbiota unveiled that GBM patients exhibited significantly higher microbial diversity compared to healthy individuals. At the phylum level, Proteobacteria saw a significant increase, while Firmicutes experienced a noteworthy decrease in the GBM group. Moving down to the family level, we observed significantly elevated levels of Enterobacteriaceae, Bacteroidaceae, and Lachnospiraceae in GBM patients, while levels of Veillonellaceae, Rikenellaceae, and Prevotellaceae were notably lower. Delving into genera statistics, we noted a substantial increase in the abundance of Parasutterella, Escherichia-Shigella, and Bacteroides, alongside significantly lower levels of Ruminococcus 2, Faecalibacterium, and Prevotella_9 in the GBM group compared to the control group. Furthermore, when examining specific species, we found a significant increase in Bacteroides vulgatus and Escherichia coli in the GBM group. These observations collectively indicate a marked dysbiosis in the gut microbial composition of GBM patients. Additionally, the GBM group exhibited notably higher levels of alpha diversity when compared to the control group. This increase in diversity suggests a significant bacterial overgrowth in the gut of GBM patients in contrast to the controls. As a result, this research opens up potential avenues to gain a better understanding of the underlying mechanisms, pathways, and potential treatments for GBM, stemming from the significant implications of gut microbial dysbiosis in these patients.

Frequency of antithyroid antibodies in patients with primary biliary cholangitis

OBJECTIVE

Primary biliary cholangitis (PBC) is an autoimmune disease of liver that may be associated with other conditions, including autoimmune thyroid diseases. We aimed to investigate the frequency of anti-thyroperoxidase antibodies (TPO-Ab), antithyroglobulin antibodies (TG-Ab), and anti-thyrotropin receptor antibodies (TSHR-Ab) in Tunisian patients with PBC.

METHODS

Sera of 80 patients with PBC were collected over a 9-year period. A total of 189 healthy blood donors (HBD) were included in the control group. Measurements of TPO-Ab and TG-Ab were performed using indirect enzyme-linked immunosorbent assay (ELISA). Competitive ELISA was used to assess TSHR-Ab.

RESULTS

Antithyroid antibodies (ATA) were significantly more frequent in PBC patients than in the control group (13.7% vs 1.6%; P < 10-3). Out of 11 patients with ATA, 10 (90.9%) were female. Nine patients and 2 HBD had TPO-Ab (11.2% vs 1%; P < 10-3). TG-Ab were more frequent in patients than in healthy subjects but the difference was not statistically significant (6.2% vs 1.6%; P = .1). TPO-Ab and TG-Ab were present together in 3 patients (3.7%). TSHR-Ab were absent in patients and controls.

CONCLUSION

This study shows that PBC is associated with a high frequency of ATA but not TG-Ab or TSHR-Ab.

Persistent bacteremia caused by Ralstonia pickettii and Microbacterium: a case report

BACKGROUND

Ralstonia pickettii is a low virulent, gram-negative bacillus that is rarely associated with human infections and may cause bacteremia. Microbacterium species are gram-positive coryneforms that are generally considered as a contaminant in Gram staining of blood cultures, especially when the time to positivity is longer than 48 h. Both these bacterial species are emerging opportunistic pathogens that may occasionally cause serious infections and even life-threatening health conditions.

CASE PRESENTATION

Here, we report the case of a patient with bacteremia caused by both R. pickettii and Microbacterium. We advocate for providers to order rapid antibiotic susceptibility testing, since our patient's suffered two kinds of rare pathogens with the opposite of drug sensitivity results to imipenem.

CONCLUSIONS

Our case present a patient suffered septic shock caused by R. pickettii and Microbacterium. Improving the antibiotic management based on the result of antimicrobial susceptibility tests is the key of successful treatment.

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.

Gluten-Free Diet Alters the Gut Microbiome in Women with Autoimmune Thyroiditis

The gut microbiome may contribute to the development of autoimmune diseases, such as autoimmune thyroiditis (AIT). Diet has a critical impact on the gut microbiome, and it has been shown that a gluten-free diet can negatively affect its composition. A gluten-free diet is popular among patients, and therefore the aim of this study was to check whether it affects thyroid function and gut microbiome composition in AIT. Thirty-one women with AIT complied with a gluten-free diet for 8 weeks. After the first 4 weeks, participants were divided into two groups: the first group received gluten in capsules and the other one-rice starch (placebo). Blood and stool samples were examined before diet (T0), after 4 weeks (T1) and after 8 weeks of diet (T2). The only significant difference in blood parameters was observed between T1 and T2 in the placebo group for the thyroid peroxidase antibody level. After the first 4 weeks, a significant increase in Desulfobacterota, Proteobacteria, Prevotella and Parasutterella and a significant decrease in Actinobacteriota, Coriobacteriaceae and Bifidobacterium were observed. The detected microbiome alterations may indicate increasing inflammation; however, further research is required, and for now, a gluten-free diet should be used cautiously in AIT.

Intestinal microbiota regulates the gut-thyroid axis: the new dawn of improving Hashimoto thyroiditis

Intestinal microbiota plays an indispensable role in the host's innate immune system, which may be related to the occurrence of many autoimmune diseases. Hashimoto thyroiditis (HT) is one of the most common autoimmune diseases, and there is plenty of evidence indicating that HT may be related to genetics and environmental triggers, but the specific mechanism has not been proven clearly. Significantly, the composition and abundance of intestinal microbiota in patients with HT have an obvious difference. This phenomenon led us to think about whether intestinal microbiota can affect the progress of HT through some mechanisms. By summarizing the potential mechanism of intestinal microflora in regulating Hashimoto thyroiditis, this article explores the possibility of improving HT by regulating intestinal microbiota and summarizes relevant biomarkers as therapeutic targets, which provide new ideas for the clinical diagnosis and treatment of Hashimoto thyroiditis.

Gut Microecology May Be Involved in the Pathogenesis of Hashimoto Thyroiditis by Reducing Production of Hydrogen Sulfide

CONTEXT

Hashimoto thyroiditis (HT) is related to intestinal microbiota alteration, but the causal relationship remains unclear. Hydrogen sulfide (H2S) is a microbiota-derived metabolite. We speculated that abnormal intestinal microbiota might limit H2S production capacity, promoting HT pathogenesis.

OBJECTIVE

This work aimed to illustrate that the intestinal microbiota plays important roles in HT pathogenesis via microbiota-derived H2S levels.

METHODS

We collected feces from HT patients and healthy donors for fecal microbiota transplantation (FMT). Thirty-six female CBA/J mice were randomly assigned to 4 groups: experimental autoimmune thyroiditis (EAT) group, EAT + Healthy group, EAT + HT group, and EAT + HT + H2S group. 16S ribosomal RNA sequencing was performed to examine gut microbiota alterations and the H2S production pathway. Serum TgAb and H2S levels were assayed by enzyme-linked immunosorbent assay and H2S-selective sensors, respectively. T-cell subpopulations in the spleen were detected by flow cytometry.

RESULTS

The gut microbiota was different after FMT among the EAT, EAT + Healthy, and EAT + HT groups. The thyroiditis score assessed by hematoxylin and eosin staining was higher in the EAT + HT group than that in the EAT and EAT + HT + H2S groups. Helper T (Th1) and Th17 cell differentiation ratios were increased in the EAT + HT group compared to the other 3 groups. Serum H2S levels were decreased and the dissimilatory sulfate reduction (DSR) pathway was attenuated in the EAT + HT group compared to the EAT + Healthy group.

CONCLUSION

H2S alleviated thyroiditis severity and related immune disorders, which were aggravated by the FMT from HT patients. The attenuated DSR pathway in the gut microbiota from HT patients might be involved in thyroiditis pathogenesis.

Investigating causal associations among gut microbiota, metabolites and autoimmune hypothyroidism: a univariable and multivariable Mendelian randomization study

Background

Accumulating evidence suggests that the gut microbiota and its metabolites may be involved in autoimmune hypothyroidism. However, the causal association between gut microbiota, metabolites and autoimmune hypothyroidism remains to be determined.

Methods

Instrumental variables were screened from the GWAS datasets of 211 gut microbiota taxonomic groups, gut microbiota-derived metabolites, and autoimmune hypothyroidism. Univariable Mendelian randomization (MR) and multivariable Mendelian randomization (MVMR) were used to analyse the potential causal relationship between autoimmune hypothyroidism, these metabolites, or these microbiota. During the MR analysis, we alternated multiple MR methods with different model assumptions to assess the consistency and robustness of the findings: inverse variance weighted (IVW), weighted median, MR pleiotropy residual sum and outlier (MRPRESSO) and MR-Egger methods. Reverse MR analysis was performed to assess the possibility of reverse causality. Finally, enrichment analyses were used to investigate potential biofunctions.

Results

The IVW results of univariable MR showed that the phyla Actinobacteria, genus DefluviitaleaceaeUCG011, genus Eggerthella, family Defluviitaleaceae, genus Subdoligranulum, genus RuminococcaceaeUCG011, and genus Intestinimonas were associated with autoimmune hypothyroidism. After FDR adjustment, the absence of a causal relationship between gut microbiota and autoimmune hypothyroidism (PFDR > 0.05) suggested a possible marginal association. The results on gut metabolites showed that N-(3-furoyl)glycine, pipecolate, phenylalanine, allantoin, indololactate and alanine were associated with autoimmune hypothyroidism. After FDR correction, only indololactate was associated with hypothyroidism (OR=1.592; 95% CI, 1.228-2.065; PFDR= 0.036). Family Defluviitaleaceae and genus DefluviitaleaceaeUCG011 were suggestively significant in the MVMR. The results of reverse MR analysis showed no reverse causality between autoimmune hypothyroidism and the identified gut microbiota. Enrichment analysis revealed that several key regulatory pathways were significantly enriched.

Conclusion

This study supported that there were beneficial or detrimental causal effects of gut microbiota and its metabolites on autoimmune hypothyroidism risk, which provides more theoretical support for mechanistic research on the "thyroid-gut" axis.

Comparative Analysis of Taxonomic and Functional Gut Microbiota Profiles in Relation to Seroconversion of Thyroid Peroxidase Antibodies in Euthyroid Participants

Background: Previous studies have reported gut microbiome alterations in Hashimoto's autoimmune thyroiditis (HT) patients. Yet, it is unknown whether an aberrant microbiome is present before clinical disease onset in participants susceptible to HT or whether it reflects the effects of the disease itself. In this study, we report for the first time a comprehensive characterization of the taxonomic and functional profiles of the gut microbiota in euthyroid seropositive and seronegative participants. Our primary goal was to determine taxonomic and functional signatures of the intestinal microbiota associated with serum thyroid peroxidase antibodies (TPOAb). A secondary aim was to determine whether different ethnicities warrant distinct reference intervals for accurate interpretation of serum thyroid biomarkers. Methods: In this cross-sectional study, euthyroid participants with (N = 159) and without (N = 1309) TPOAb were selected from the multiethnic (European Dutch, Moroccan, and Turkish) HEalthy Life In an Urban Setting (HELIUS) cohort. Fecal microbiota composition was profiled using 16S rRNA sequencing. Differences between the groups were analyzed based on the overall composition (alpha and beta diversity), as well as differential abundance (DA) of microbial taxa and functional pathways using multiple DA tools. Results: Overall composition showed a substantial overlap between the two groups (p > 0.05 for alpha-diversity; p = 0.39 for beta-diversity), indicating that TPOAb-seropositivity does not significantly differentiate gut microbiota composition and diversity. Interestingly, TPOAb status accounted for only a minor fraction (0.07%) of microbiome variance (p = 0.545). Further exploration of taxonomic differences identified 138 taxa nominally associated with TPOAb status. Among these, 13 taxa consistently demonstrated nominal significance across three additional DA methods, alongside notable associations within various functional pathways. Furthermore, we showed that ethnicity-specific reference intervals for serum thyroid biomarkers are not required, as no significant disparities in serum thyroid markers were found among the three ethnic groups residing in an iodine-replete area (p > 0.05 for thyrotropin, free thyroxine, and TPOAb). Conclusion: These findings suggest that there is no robust difference in gut microbiome between individuals with or without TPOAb in terms of alpha and beta-diversity. Nonetheless, several taxa were identified with nominal significance related to TPOAb presence. Further research is required to determine whether these changes indeed imply a higher risk of overt HT.

Causal analysis of the gut microbiota in differentiated thyroid carcinoma: a two-sample Mendelian randomization study

Objective: Numerous studies have highlighted an association between the gut microbiota (GM) and thyroid tumors. Employing Mendelian randomization methodology, we seek to elucidate the causal link between the gut microbiota and thyroid neoplasms. Methods: We procured data from the Mibiogen database encompassing 211 distinct gut microbiota taxa, alongside extensive genome-wide association studies (GWAS) summary data for differentiated thyroid carcinoma (DTC). Our principal analytical approach involved the application of the Inverse-Variance Weighted method (IVW) within the framework of Mendelian randomization. Simultaneously, we conducted sensitivity analyses to assess result heterogeneity, horizontal pleiotropy, and outcome stability. Results: IVW analysis revealed a dual role of the GM in thyroid carcinoma. The phylum Actinobacteria (OR, 0.249 [95% CI, 0.121-0.515]; p < 0.001) was associated with a decreased risk of DTC. Conversely, the genus Ruminiclostridium9 (OR, 11.276 [95% CI, 4.406-28.860]; p < 0.001), class Mollicutes (OR, 5.902 [95% CI, 1.768-19.699]; p = 0.004), genus RuminococcaceaeUCG004 (OR, 3.831 [95% CI, 1.516-9.683]; p = 0.005), genus Paraprevotella (OR, 3.536 [95% CI, 1.330-9.401]; p = 0.011), and phylum Tenericutes (OR, 5.902 [95% CI, 1.768-19.699]; p = 0.004) were associated with an increased risk of DTC. Conclusion: Our findings underscore that the presence of genus Ruminiclostridium9, class Mollicutes, genus RuminococcaceaeUCG004, genus Paraprevotella, and phylum Tenericutes is associated with an elevated risk of DTC, whereas the presence of the phylum Actinobacteria is linked to a decreased risk. These discoveries enhance our comprehension of the relationship between the GM and DTC.

Thyroid Diseases and Intestinal Microbiome

The human microbiome plays an integral role in health. In particular, it is important for the development, differentiation, and maturation of the immune system, 70% of which resides in the intestinal mucosa. Microbiome studies conducted to date have revealed an association between disturbances in the microbiota (dysbiosis) and various pathological disorders, including changes in host immune status. Autoimmune thyroid diseases are one of the most common organ-specific autoimmune disorders, with a worldwide prevalence higher than 5%. The predominant autoimmune thyroid diseases are Hashimoto's thyroiditis and Grave's disease. Several factors, such as genetic and environmental ones, have been studied. In accordance with recent studies, it is assumed that the gut microbiome might play a significant role in triggering autoimmune diseases of the thyroid gland. However, the exact etiology has not yet been elucidated. The present review aims to describe the work carried out so far regarding the role of gut microflora in the pathogenesis of autoimmune thyroid diseases and its involvement in the appearance of benign nodules and papillary thyroid cancer. It appears that future work is needed to elucidate more precisely the mechanism for gut microbiota involvement in the development of autoimmune thyroid diseases.

Complex relationship between gut microbiota and thyroid dysfunction: a bidirectional two-sample Mendelian randomization study

Background

Many studies have reported the link between gut microbiota and thyroid dysfunction. However, the causal effect of gut microbiota on thyroid dysfunction and the changes in gut microbiota after the onset of thyroid dysfunction are not clear.

Methods

A two-sample Mendelian randomization (MR) study was used to explore the complex relationship between gut microbiota and thyroid dysfunction. Data on 211 bacterial taxa were obtained from the MiBioGen consortium, and data on thyroid dysfunction, including hypothyroidism, thyroid-stimulating hormone alteration, thyroxine deficiency, and thyroid peroxidase antibodies positivity, were derived from several databases. Inverse variance weighting (IVW), weighted median, MR-Egger, weighted mode, and simple mode were applied to assess the causal effects of gut microbiota on thyroid dysfunction. Comprehensive sensitivity analyses were followed to validate the robustness of the results. Finally, a reverse MR study was conducted to explore the alteration of gut microbiota after hypothyroidism onset.

Results

Our bidirectional two-sample MR study revealed that the genera Intestinimonas, Eubacterium brachy group, Ruminiclostridium5, and Ruminococcaceae UCG004 were the risk factors for decreased thyroid function, whereas the genera Bifidobacterium and Lachnospiraceae UCG008 and phyla Actinobacteria and Verrucomicrobia were protective. The abundance of eight bacterial taxa varied after the onset of hypothyroidism. Sensitivity analysis showed that no heterogeneity or pleiotropy existed in the results of this study.

Conclusion

This novel MR study systematically demonstrated the complex relationship between gut microbiota and thyroid dysfunction, which supports the selection of more targeted probiotics to maintain thyroid-gut axis homeostasis and thus to prevent, control, and reverse the development of thyroid dysfunction.

Exploring the role of gut microbiota in autoimmune thyroid disorders: a systematic review and meta-analysis

Background

Autoimmune thyroid diseases (AITDs) are characterized by unique immune responses against thyroid antigens and persist over time. The most common types of AITDs are Graves' disease (GD) and Hashimoto's thyroiditis (HT). There is mounting evidence that changes in the microbiota may play a role in the onset and development of AITDs.

Objective

The purpose of this comprehensive literature study was to answer the following query: Is there a difference in microbiota in those who have AITDs?

Methods

According to the standards set out by the PRISMA statement, 16 studies met the requirements for inclusion after being screened for eligibility.

Results

The Simpson index was the only diversity measure shown to be considerably lower in patients with GD compared to healthy participants, whereas all other indices were found to be significantly greater in patients with HT. The latter group, however, showed a greater relative abundance of Bacteroidetes and Actinobacteria at the phylum level, and consequently of Prevotella and Bifidobacterium at the genus level. The strongest positive and negative relationships were seen for thyroid peroxidase antibodies and bacterial load.

Conclusion

Overall, both GD and HT patients showed significant changes in the gut microbiota's diversity and composition.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42023432455.

Exploring the Association Between Thyroid Function and Oral Microbiome Diversity: An NHANES Analysis

Objective

To investigate the association between thyroid functions and the oral microbiome diversity.

Method

Data from the US National Health and Nutrition Examination Survey (NHANES; 2009-2012) were analyzed. Thyroid functions were defined using thyroid hormones and related biomarkers. Oral microbiome was measured using the observed number of amplicon sequence variants (ASVs) and the Bray-Curtis dissimilarity. Linear regression was used to estimate the average change (β) and 95% CI for the number of ASVs against thyroid functions, adjusted for sociodemographic variables, health conditions, urinary iodine status, and periodontitis. Non-metric multidimensional scaling (NMDS) was used to analyze the Bray-Curtis dissimilarity.

Results

A total of 2943 participants were analyzed. The observed number of ASVs has a weighted mean of 128.9. Self-reported thyroid disease was associated with reduced number of ASVs (β = -9.2, 95% CI: -17.2, -1.2), if only adjusted for sociodemographic variables and health conditions. In the fully adjusted model, compared to normal thyroid function, both subclinical and clinical hyperthyroidism were associated with reduced number of ASVs (β = -59.6, 95% CI: -73.2, -46.0; β = -28.2, 95% CI: -50.0, -6.5, respectively). Thyroid peroxidase antibody level higher than the reference range was associated with higher observed ASV (β= 9.0, 95% CI: 1.2, 16.9). NMDS analysis suggested significant difference in oral microbiome composition between free triiodothyronine groups (P = .002), between free thyroxine groups (P = .015), and between thyroglobulin groups (P = .035).

Conclusion

Hyperthyroidism was associated with reduced oral microbiome diversity. Free triiodothyronine, free thyroxine, and thyroglobulin levels may alter the oral microbiome composition.

Protocol for a double-blinded randomised controlled trial to assess the effect of faecal microbiota transplantations on thyroid reserve in patients with subclinical autoimmune hypothyroidism in the Netherlands: the IMITHOT trial

BACKGROUND

Hashimoto's thyroiditis (HT) is a common endocrine autoimmune disease affecting roughly 5% of the general population and involves life-long treatment with levothyroxine, as no curative treatment yet exists. Over the past decade, the crosstalk between gut microbiota and the host immune system has been well-recognised, identifying the gut microbiome as an important factor in host health and disease, including susceptibility to autoimmune diseases. Previous observational studies yielded a link between disruption of the gut microbiome composition and HT. This is the first study that investigates the potential of restoring a disrupted gut microbiome with faecal microbiota transplantations (FMTs) to halt disease progression and dampen autoimmunity.

METHODS AND ANALYSIS

The IMITHOT trial is a randomised, double-blinded, placebo-controlled study evaluating either autologous or allogenic FMTs in medication-naïve patients with subclinical autoimmune hypothyroidism. In total, 34 patients will be enrolled to receive either three allogenic or autologous FMTs. FMT will be made of fresh stool and directly administered into the duodenum. Patients will be evaluated at baseline before the first FMT is administered and at 6, 12 and 24 months post-intervention to assess efficacy and adverse events. The primary outcome measure will be the net incremental increase (incremental area under the curve) on thyrotropin-stimulated free thyroxine and free triiodothyronine release at 6 and 12 months compared with baseline. Results will be disseminated via peer-reviewed journals and international conferences. The recruitment of the first patient and donor occurred on 18 December 2019.

ETHICS AND DISSEMINATION

Ethics approval was obtained from the hospital Ethics Committee (Medical Ethics Committee) at Amsterdam University Medical Center. The trial's outcomes offer high-quality evidence that aids in unveiling distinct patterns within the gut microbiota potentially associated with improved thyroid function. Consequently, this may open avenues for the future clinical applications of microbial-targeted therapy in individuals at risk of developing overt HT.

TRIAL REGISTRATION NUMBER

NL7931.

Correlation between gut microbiota and the development of Graves' disease: A prospective study

The association between gut microbiota and development of Graves' disease (GD) remains unclear. This study aimed to profile the gut microbiota of 65 patients newly diagnosed with GD before and after treatment and 33 physical examination personnel via 16S rRNA sequencing. Significant differences in the gut microbiota composition were observed between the two groups, showing relative bacterial abundances of 1 class, 1 order, 5 families, and 14 genera. After treatment, the abundance of the significantly enriched biota in the GD group decreased considerably, whereas that of the previously decreased biota increased considerably. Further, interleukin-17 levels decreased significantly. The random forest method was used to identify 12 genera that can distinguish patients with GD from healthy controls. Our study revealed that the gut microbiota of patients with GD exhibit unique characteristics compared with that of healthy individuals, which may be related to an imbalance in the immune system and gut microbiota.

Gut Microbiome Associated With Graves Disease and Graves Orbitopathy: The INDIGO Multicenter European Study

CONTEXT

Gut bacteria can influence host immune responses but little is known about their role in tolerance-loss mechanisms in Graves disease (GD; hyperthyroidism caused by autoantibodies, TRAb, to the thyrotropin receptor, TSHR) and its progression to Graves orbitopathy (GO).

OBJECTIVE

This work aimed to compare the fecal microbiota in GD patients, with GO of varying severity, and healthy controls (HCs).

METHODS

Patients were recruited from 4 European countries (105 GD patients, 41 HCs) for an observational study with cross-sectional and longitudinal components.

RESULTS

At recruitment, when patients were hyperthyroid and TRAb positive, Actinobacteria were significantly increased and Bacteroidetes significantly decreased in GD/GO compared with HCs. The Firmicutes to Bacteroidetes (F:B) ratio was significantly higher in GD/GO than in HCs. Differential abundance of 15 genera was observed in patients, being most skewed in mild GO. Bacteroides displayed positive and negative correlations with TSH and free thyroxine, respectively, and was also significantly associated with smoking in GO; smoking is a risk factor for GO but not GD. Longitudinal analyses revealed that the presence of certain bacteria (Clostridiales) at diagnosis correlated with the persistence of TRAb more than 200 days after commencing antithyroid drug treatment.

CONCLUSION

The increased F:B ratio observed in GD/GO mirrors our finding in a murine model comparing TSHR-immunized with control mice. We defined a microbiome signature and identified changes associated with autoimmunity as distinct from those due to hyperthyroidism. Persistence of TRAb is predictive of relapse; identification of these patients at diagnosis, via their microbiome, could improve management with potential to eradicate Clostridiales.

Alteration of Intestinal Microbiota and Hydrogen Sulfide Metabolism in Patients with Hashimoto's Thyroiditis

Objective

To analyze the intestinal microbiota and H2S levels in patients with HT.

Methods

Twenty euthyroid HT patients and twenty healthy control individuals were recruited. Fecal samples were collected, and the microbiota was examined using 16S RNA gene sequencing. We also collected serum samples to examine the H2S levels.

Results

Compared with patients with HT, the ACE and Chao indices were significantly lower in healthy controls (P=0.04, 0.03, respectively). The microbial composition of the HT group differed significantly from that of the healthy group. We observed a significant increase in the proportions of Bacteroides, Fusobacterium, Sutterella, and Veillonella in patients with HT (P < 0.05). Linear discriminant analysis and effect size analysis also revealed that Bacteroides and Ralstonia were enriched in patients with HT. Additionally, patients with HT had significantly lower H2S levels than healthy controls (P < 0.005). The enrichment of H2S anabolism was linked to the alteration of intestinal microbiota in patients with HT.

Conclusion

We demonstrated that patients with HT have aberrant intestinal microbiome and that H2S anabolism may contribute to HT pathogenesis.

Gut microbiota short-chain fatty acids and their impact on the host thyroid function and diseases

Thyroid disorders are clinically characterized by alterations of L-3,5,3',5'-tetraiodothyronine (T4), L-3,5,3'-triiodothyronine (T3), and/or thyroid-stimulating hormone (TSH) levels in the blood. The most frequent thyroid disorders are hypothyroidism, hyperthyroidism, and hypothyroxinemia. These conditions affect cell differentiation, function, and metabolism. It has been reported that 40% of the world's population suffers from some type of thyroid disorder and that several factors increase susceptibility to these diseases. Among them are iodine intake, environmental contamination, smoking, certain drugs, and genetic factors. Recently, the intestinal microbiota, composed of more than trillions of microbes, has emerged as a critical player in human health, and dysbiosis has been linked to thyroid diseases. The intestinal microbiota can affect host physiology by producing metabolites derived from dietary fiber, such as short-chain fatty acids (SCFAs). SCFAs have local actions in the intestine and can affect the central nervous system and immune system. Modulation of SCFAs-producing bacteria has also been connected to metabolic diseases, such as obesity and diabetes. In this review, we discuss how alterations in the production of SCFAs due to dysbiosis in patients could be related to thyroid disorders. The studies reviewed here may be of significant interest to endocrinology researchers and medical practitioners.

Faecalibacterium prausnitzii in Differentiated Thyroid Cancer Patients Treated with Radioiodine

BACKGROUND

Faecalibacterium prausnitzii, one of the most important bacteria of the human gut microbiota, produces butyrate (a short-chain fatty acid). Short-chain fatty acids are known to influence thyroid physiology and thyroid cancer's response to treatment. We aimed to analyze the relative abundance of Faecalibacterium prausnitzii on the gut microbiota of differentiated thyroid cancer patients compared to controls and its variation after radioiodine therapy (RAIT).

METHODS

Fecal samples were collected from 37 patients diagnosed with differentiated thyroid cancer before and after radioiodine therapy and from 10 volunteers. The abundance of F. prausnitzii was determined using shotgun metagenomics.

RESULTS

Our study found that the relative abundance of F. prausnitzii is significantly reduced in thyroid cancer patients compared to volunteers. We also found that there was a mixed response to RAIT, with an increase in the relative and absolute abundances of this bacterium in most patients.

CONCLUSIONS

Our study confirms that thyroid cancer patients present a dysbiotic gut microbiota, with a reduction in F. prausnitzii's relative abundance. In our study, radioiodine did not negatively affect F. prausnitzii, quite the opposite, suggesting that this bacterium might play a role in resolving radiation aggression issues.

Yijung-tang improves thermogenesis and reduces inflammation associated with gut microbiota in hypothyroid rats

Currently, considerable attention is focused on exploring the potential relationship between herbal medicine (HM) and the gut microbiome in terms of thermoregulation, which is an important aspect of human health, in modern system biology. However, our knowledge of the mechanisms of HM in thermoregulation is inadequate. Here, we demonstrate that the canonical herbal formula, Yijung-tang (YJT), protects against hypothermia, hyperinflammation, and intestinal microbiota dysbiosis in PTU-induced hypothyroid rats. Notably, these properties were associated with alterations in the gut microbiota and signaling crosstalk between the thermoregulatory and inflammatory mediators in the small intestine and brown adipose tissue (BAT). In contrast to the conventional drug L-thyroxine for curing hypothyroidism, YJT has an efficacy for attenuating systematic inflammatory responses, related with depression in intestinal TLR4 and Nod2/Pglyrp1 signaling pathways. Our findings suggest that YJT could promote BAT thermogenesis and prevent systemic inflammation in PTU-induced hypothyroid rats, which was associated with its prebiotic effect on modulating of the gut microbiota and gene expression with relevance in the enteroendocrine function and innate immune systems. These findings may strengthen the rationale of the microbiota-gut-BAT axis for a paradigm shift to enable holobiont-centric medicine.

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.

Evolving interplay between natural products and gut microbiota

Growing evidence suggests gut microbiota status affects human health, and microbiota imbalance will induce multiple disorders. Natural products are gaining increasing attention for their therapeutical effects and less side effects. The emerging studies support that the activities of many natural products are dependent on gut microbiota, meanwhile gut microbiota is modulated by natural products. In this review, we summarized the interplay between the gut microbiota and host disease, and the emerging molecular mechanisms of the interaction between natural products and gut microbiota. Focusing on gut microbiota metabolite of various natural products, and the effects of natural products on gut microbiota, we summarized the biotransformation pathways of natural products, and discussed the effect of natural products on the composition modulation of gut microbiota, protection of gut mucosal barrier and modulation of the gut microbiota metabolites. Dissecting the interplay between gut microbiota and natural products will help elucidate the therapeutic mechanisms of natural products.

A Comprehensive Review of Thyroid Hormone Metabolism in the Gut and Its Clinical Implications

Background: The gut is a target organ of thyroid hormone (TH) that exerts its action via the nuclear thyroid hormone receptor α1 (TRα1) expressed in intestinal epithelial cells. THs are partially metabolized via hepatic sulfation and glucuronidation, resulting in the production of conjugated iodothyronines. Gut microbiota play an important role in peripheral TH metabolism as they produce and secrete enzymes with deconjugation activity (β-glucuronidase and sulfatase), via which TH can re-enter the enterohepatic circulation. Summary: Intestinal epithelium homeostasis (the finely tuned balance between cell proliferation and differentiation) is controlled by the crosstalk between triiodothyronine and TRα1 and the presence of specific TH transporters and TH-activating and -inactivating enzymes. Patients and experimental murine models with a dominant-negative mutation in the TRα exhibit gross abnormalities in the morphology of the intestinal epithelium and suffer from severe symptoms of a dysfunctional gastrointestinal tract. Over the past decade, gut microbiota has been identified as an essential factor in health and disease, depending on its compositional and functional profile. This has led to a renewed interest in the so-called gut-thyroid axis. Disruption of gut microbial homeostasis (dysbiosis) is associated with autoimmune thyroid disease (AITD), including Hashimoto's thyroiditis, Graves' disease, and Graves' orbitopathy. These studies reviewed here provide new insights into the gut microbiota roles in thyroid disease pathogenesis and may be an initial step toward microbiota-based therapies in AITD. However, it should be noted that cause-effect mechanisms remain to be proven, for which prospective cohort studies, randomized clinical trials, and experimental studies are needed. Conclusion: This review aims at providing a comprehensive insight into the interplay between TH metabolism and gut homeostasis.

Hashimoto's thyroiditis and coexisting disorders in correlation with HLA status-an overview

Hashimoto's thyroiditis (HT), also known as chronic lymphocytic thyroiditis, is a frequent disorder of the thyroid gland caused by autoimmune-trigged lymphocytic infiltration and destruction of the thyroid gland. With the progressive destruction of the organ, the thyroid gland shrinks in size, thus commonly leading to hypothyroidism. Therapy of HT is mainly focused on managing the thyroid dysfunction by oral substitution of L‑thyroxine. However, patients with HT often complain about a broad spectrum of symptoms, with some of them hardly explained by HT itself. Several other disorders are known to be associated with HT. The etiology of HT seems to be multifactorial, including environmental influences such as iodine supply, infections, and stress as triggers of immune modulation. In addition, also a genetic background based on changes of the human leukocyte antigen (HLA) status seems to be evident. The paper will provide an overview of diseases related to HT, including their correlation to certain HLA patterns. This presentation should give a broader view on HT-related disorders and facilitate detailed examination and management of patients with HT.

Alterations of the gut microbiota in type 2 diabetics with or without subclinical hypothyroidism

Background

Diabetes and thyroid dysfunction are two closely related endocrine diseases. Increasing evidences show that gut microbiota plays an important role in both glucose metabolism and thyroid homeostasis. Meanwhile, copy number variation (CNV) of host salivary α-amylase gene (AMY1) has been shown to correlate with glucose homeostasis. Hence, we aim to characterize the gut microbiota and CNV of AMY1 in type 2 diabetes (T2D) patients with or without subclinical hypothyroidism (SCH).

Methods

High-throughput sequencing was used to analyze the gut microbiota of euthyroid T2D patients, T2D patients with SCH and healthy controls. Highly sensitive droplet digital PCR was used to measure AMY1 CN.

Results

Our results revealed that T2D patients have lower gut microbial diversity, no matter with or without SCH. The characteristic taxa of T2D patients were Coriobacteriales, Coriobacteriaceae, Peptostreptococcaceae, Pseudomonadaceae, Collinsella, Pseudomonas and Romboutsia. Meanwhile, Escherichia/Shigella, Lactobacillus_Oris, Parabacteroides Distasonis_ATCC_8503, Acetanaerobacterium, Lactonifactor, uncultured bacterium of Acetanaerobacterium were enriched in T2D patients with SCH. Moreover, serum levels of free triiodothyronine (FT3) and free thyroxine (FT4) in T2D patients were both negatively correlated with richness of gut microbiota. A number of specific taxa were also associated with clinical parameters at the phylum and genus level. In contrast, no correlation was found between AMY1 CN and T2D or T2D_SCH.

Conclusion

This study identified characteristic bacterial taxa in gut microbiota of T2D patients with or without SCH, as well as the taxa associated with clinical indices in T2D patients. These results might be exploited in the prevention, diagnosis and treatment of endocrine disorders in the future.

What we know about the relationship between autoimmune thyroid diseases and gut microbiota: a perspective on the role of probiotics on pediatric endocrinology

INTRODUCTION

Autoimmune diseases account for a cumulative overall prevalence of about 3-5% worldwide. Among them, autoimmune thyroid diseases (ATDs) are the most common and comprise two main entities: Hashimoto's thyroiditis (HT) and Graves-Basedow disease (GD). The pathogenesis of ATDs remains not fully elucidated, however the role of microbioma has been proposed. Gut microbiota exert an important influence on the intestinal barrier, nutrient metabolism and immune system development and functions.

EVIDENCE ACQUISITION

In this review, we describe on the main features of ATDs in pediatrics, focusing on the reciprocal influence between gut microbiota, thyroid hormone metabolism and thyroid autoimmunity and consider the role of probiotics and other microbiota-targeted therapies in thyroid diseases with a perspective on pediatric endocrinology.

EVIDENCE SYNTHESIS

Microbiome affects both endogenous and exogenous thyroid hormone metabolism and influences the absorption of minerals important to the thyroid function, which are iodine, selenium, zinc and iron. The alteration of the gut microbiota, with the consequent modifications in the barrier function and the increased gut permeability, seems involved in the development of autoimmune and chronic inflammatory diseases, including ATDs. The supplementation with probiotics showed beneficial effects on the thyroid hormone and thyroid function because this strategy could restore the intestinal eubiosis and the good strain microorganism proliferation.

CONCLUSIONS

Even though the evidence about the interaction between microbiota and ATDs in pediatric patients is limited, the promising results obtained in the adult population, and in other autoimmune disorders affecting children, highlight the need of for further research in the pediatric field.

A Chinese herbs complex ameliorates gut microbiota dysbiosis induced by intermittent cold exposure in female rats

Cold is a common source of stress in the alpine areas of northern China. It affects the microbial community, resulting in the invasion of pathogenic microorganisms and intestinal diseases. In recent years, studies have reported that Chinese herbal extracts and their fermentation broth have a significant beneficial effect on gut microbiota. This study aimed to investigate the probiotic effect of a self-designed Chinese herbs complex on the gut microbiota of rats exposed to cold. The rats were treated with intermittent cold exposure and Chinese herbs complex for 14 days, and the gut microbiota composition and other parameters were assayed. The 16s ribosomal DNA high-throughput sequencing and analysis confirmed that the Chinese herbs complex positively improved the gut microbiota. We found that cold exposure could lead to significant changes in the composition of gut microbiota, and affect the intestinal barrier and other physiological functions. The relative abundance of some probiotics in the genus such as Roseburia, Parasutterella, and Elusimicrobium in rats treated with Chinese herbs complex was significantly increased. Serum D-lactic acid (D-LA) and lipopolysaccharide (LPS) were increased in the cold exposure group and decreased in the Chinese herbs complex-treated group. Moreover, the Chinese herbs complex significantly increased the protein expression of occludin. In conclusion, the Chinese herbs complex is effective in restoring the gut microbiota caused by cold exposure, improving the function of the intestinal barrier, and may act as a prebiotic in combatting gut dysbiosis.

Microbiota Alterations in Patients with Autoimmune Thyroid Diseases: A Systematic Review

Autoimmune thyroid diseases (AITDs) are chronic autoimmune disorders that cause impaired immunoregulation, leading to specific immune responses against thyroid antigens. Graves' disease (GD) and Hashimoto's thyroiditis (HT) are the major forms of AITDs. Increasing evidence suggests a possible role of microbiota alterations in the pathogenesis and progression of AITDs. This systematic review was designed to address the following question: "Is microbiota altered in patients with AITDs?" After screening the selected studies using the inclusion and exclusion criteria, 16 studies were included in this review (in accordance with PRISMA statement guidelines). A meta-analysis revealed that patients with HT showed significantly higher values of diversity indices (except for the Simpson index) and that patients with GD showed significant tendencies toward lower values of all assessed indices compared with healthy subjects. However, the latter demonstrated a higher relative abundance of Bacteroidetes and Actinobacteria at the phylum level and thus Prevotella and Bifidobacterium at the genus level, respectively. Thyroid peroxidase antibodies showed the most significant positive and negative correlations between bacterial levels and thyroid functional parameters. In conclusion, significant alterations in the diversity and composition of the intestinal microbiota were observed in both GD and HT patients.

Oxidative stress in Hashimoto's thyroiditis: possible adjuvant therapies to attenuate deleterious effects

A number of studies have shown that oxidative stress is related to the pathogenesis of several immunological diseases, such as Hashimoto's thyroiditis (HT), although there is no plausible mechanism to explain it. Thus, we aimed at hypothesizing and providing some possible mechanisms linking oxidative stress to autoimmunity aspects and its implications for HT, as well as adjuvant therapeutic proposals to mitigate the deleterious effects. Our hypothesis is that deficient eating habits, autoimmune regulator gene predisposing gene, dysbiosis and molecular mimicry, unfolded proteins and stress in the endoplasmic reticulum, and thymus involution appear to be the main potential factors leading to HT oxidative stress. Likewise, we show that the use of minerals selenium and zinc, vitamins D and C, as well as probiotics, can be interesting adjuvant therapies for the control of oxidative damage and poor prognosis of HT. Further clinical trials are needed to understand the real beneficial and side effects of these supplements.

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.

Metabolic Characteristics of Hashimoto's Thyroiditis Patients and the Role of Microelements and Diet in the Disease Management-An Overview

Hashimoto’s thyroiditis (HT) is the most common autoimmune disease and the leading cause of hypothyroidism, in which damage to the thyroid gland occurs due to the infiltration of lymphocytes. It is characterized by increased levels of antibodies against thyroid peroxidase and thyroglobulin. In this review, we present the metabolic profile, the effectiveness of micronutrient supplementation and the impact of dietary management in patients with HT. For this current literature review, the databases PubMed, Cochrane, Medline and Embase were reviewed from the last ten years until March 2022. This article provides a comprehensive overview of recent randomized controlled trials, meta-analyses, and clinical trials. Many patients with HT, even in the euthyroid state, have excess body weight, metabolic disorders, and reduced quality of life. Due to frequent concomitant nutritional deficiencies, the role of vitamin D, iodine, selenium, magnesium, iron and vitamin B12 is currently debated. Several studies have underlined the benefits of vitamin D and selenium supplementation. There is still no specific diet recommended for patients with HT, but a protective effect of an anti-inflammatory diet rich in vitamins and minerals and low in animal foods has been suggested. There is insufficient evidence to support a gluten-free diet for all HT patients. Pharmacotherapy, along with appropriate nutrition and supplementation, are important elements of medical care for patients with HT. The abovementioned factors may decrease autoantibody levels, improve thyroid function, slow down the inflammatory process, maintain proper body weight, relieve symptoms, and prevent nutritional deficiencies and the development of metabolic disorders in patients with HT.

Interaction of Gut Microbiota with Endocrine Homeostasis and Thyroid Cancer

The gut microbiota plays a crucial role in healthy individuals as well as in patients with thyroid diseases, including thyroid cancer. Although the prognosis of differentiated thyroid cancer is predictable, that of some poorly differentiated, medullary, and anaplastic thyroid cancers remains unpromising. As the interaction between the gut microbiota and thyroid cancer has been gradually revealed in recent years, the thyroid gland, a crucial endocrine organ, is shown to have a complex connection with the body's metabolism and is involved in inflammation, autoimmunity, or cancer progression. Dysbiosis of the gut microbiota and its metabolites can influence changes in hormone levels and susceptibility to thyroid cancer through multiple pathways. In this review, we focus on the interactions of the gut microbiota with thyroid function diseases and thyroid cancer. In addition, we also discuss some potential new strategies for the prevention and treatment of thyroid disease and thyroid cancer. Our aim is to provide some possible clinical applications of gut microbiota markers for early diagnosis, treatment, and postoperative management of thyroid cancer. These findings were used to establish a better multi-disciplinary treatment and prevention management strategy and to individualize the treatment of patients in relation to their gut microbiota composition and pathological characteristics.

The relationships between the gut microbiota and its metabolites with thyroid diseases

Emerging studies have provided a preliminary understanding of the thyroid-gut axis, indicating that intestinal microbiota and its metabolites may act directly or indirectly on the thyroid by influencing intestinal microelements uptake, iodothyronine conversion and storage, and immune regulation, providing new insights into the pathogenesis of thyroid disorders and clinical management strategies. However, the research on gut microbiota and thyroid has only presented the tip of the iceberg. More robust clinical data and basic experiments are still required to elucidate the specific relationships and mechanisms in the future. Here we will characterize the associations between the microbiota and thyroid diseases to evaluate their potential implications in the pathophysiology and open up scientific avenues for future precision studies of the thyroid-gut axis.

Gut microbial dysbiosis and its association with esophageal cancer

Due to its aggressive nature and low survival rate, esophageal cancer is one of the deadliest cancer. While the intestinal microbiome significantly influences human health and disease. This research aimed to investigate and characterize the relative abundance of intestinal bacterial composition in esophageal cancer patients. The fecal samples were collected from esophageal cancer patients (n = 15) and healthy volunteers (n = 10). The PCR-DGGE was carried out by focusing on the V3 region of the 16S rRNA gene, and qPCR was performed for Bacteroides vulgatus, Escherichia coli, Bifidobacterium, Clostridium leptum and Lactobacillus. High-throughput sequencing of the 16S rRNA gene targeting the V3+V4 region was performed on 20 randomly selected samples. PCR-DGGE and High-throughput diversity results showed a significant alteration of gut bacterial composition between the experimental and control groups, which indicates the gut microbial dysbiosis in esophageal cancer patients. At the phylum level, there was significant enrichment of Bacteroidetes, while a non-significant decrease of Firmicutes in the experimental group. At family statistics, a significantly higher level of Bacteroidaceae and Enterobacteriaceae, while a significantly lower abundance of Prevotellaceae and Veillonellaceae were observed. There was a significantly high prevalence of genera Bacteroides, Escherichia-Shigella, while a significantly lower abundance of Prevotella_9 and Dialister in the experimental group as compared to the control group. Furthermore, the species analysis also showed significantly raised level of Bacteroides vulgatus and Escherichia coli in the experimental group. These findings revealed a significant gut microbial dysbiosis in esophageal cancer patients. So, the current study can be used for the understanding of esophageal cancer treatment, disease pathway, mechanism, and probiotic development.

Simulation Model for Hashimoto Autoimmune Thyroiditis Disease

Hashimoto thyroiditis (HT) is a pathology that often causes a gradual thyroid insufficiency in affected patients due to the autoimmune destruction of this gland. The cellular immune response mediated by T helper lymphocytes TH1 and TH17 can induce the HT disease. In this pathologic condition, there is an imbalance between the TH17 and Treg lymphocytes as well as a gut microbiota dysfunction. The objective of this work was to describe the interactions of the cell subpopulations that participate in HT. To achieve this goal, we generated a mathematical model that allowed the simulation of different scenarios for the dynamic interaction between thyroid cells, the immune system, and the gut microbiota. We used a hypothetical-deductive design of mathematical modeling based on a system of ordinary differential equations, where the state variables are the TH1, TH17, and Treg lymphocytes, the thyrocytes, and the bacteria from gut microbiota. This work generated a compartmental model of the cellular immune response occurring in the thyroid gland. It was observed that TH1 and TH17 lymphocytes could increase the immune cells' activity, as well as activate effector cells directly and trigger the apoptosis and inflammation processes of healthy thyrocytes indirectly. Likewise, the model showed that a reduction in Treg lymphocytes could increase the activity of TH17 lymphocytes when an imbalance of the gut microbiota composition occurred. The numerical results highlight the TH1, TH17, and bacterial balance of the gut microbiota activities as important factors for the development of HT disease.

Effects of the Sex Factor on Mouse Iodine Intake: Interactions between the Gut Microbiota Composition and Metabolic Syndromes

Iodine plays a key role in maintaining thyroid homeostasis, which is influenced by hormones through almost all nucleated cells and is essential for growth and metabolism. The most common kinds of thyroid dysfunction, hypothyroidism and hyperthyroidism, are markedly related to iodine intake. In addition, the prevalence and incidence of hypothyroidism and hyperthyroidism are much higher in women than in men. However, the association between thyroid homeostasis and the gut microbiota is not yet completely clear, especially when comparing women and men. In this study, differences in the gut microbiota compositions, metabolic syndromes, and molecular mechanisms of female and male mice were investigated after iodine supplementation. The gut microbiota in male mice was changed more than that of female mice. The abundances of Muribacium intestinale, Barnesiella, Alloprevotella, Enterococcus, Desulfovibrionaceae, and Clostridium were significantly increased in female mice. This finding indicates that the high risk of thyroid disease in women could be related to the gut microbiota composition.

Oral Microbiota Composition and Function Changes During Chronic Erythematous Candidiasis

Oral microbiota is constantly changing with the host state, whereas the oral microbiome of chronic erythematous candidiasis remains poorly understood. The aim of this study was to compare oral microbial signatures and functional profiling between chronic erythematous candidiasis and healthy subjects. Using shotgun metagenomic sequencing, we analyzed the microbiome in 12 chronic erythematous candidiasis, 12 healthy subjects, and 2 chronic erythematous candidiasis cured by antifungal therapy. We found that the salivary microbiota of chronic erythematous candidiasis was significantly different from that of healthy subjects. Among them, Rothia mucilaginosa and Streptococcus mitis were the most abundant disease-enriched species (Mann-Whitney U-test, P < 0.05). In addition, co-occurrence network analysis showed that C. albicans formed densely connected modules with oral bacterial species and was mainly positive connected to Streptococcus species. Furthermore, we investigated the functional potentials of the microbiome and identified a set of microbial marker genes associated with chronic erythematous candidiasis. Some of these genes enriching in chronic erythematous candidiasis are involved in eukaryotic ribosome, putative glutamine transport system, and cytochrome bc1 complex respiratory unit. Altogether, this study revealed the changes of oral microbial composition, the co-occurrence between C. albicans and oral bacteria, as well as the changes of microbial marker genes during chronic erythematous candidiasis, which provides evidence of oral microbiome as a target for the treatment and prevention of chronic erythematous candidiasis.

Microbiome Metabolites and Thyroid Dysfunction

Thyroid diseases are common conditions that have a negative impact on the health of all populations. The literature sheds light on the differences in the composition of the intestinal microbiota in patients suffering from thyroid diseases compared to healthy individuals. The microbiome affects the proper functioning of the thyroid gland, and the existence of the gut–thyroid axis is discussed in the context of both thyroid diseases and intestinal dysbiosis. The purpose of this review is to describe associations between the microbiome and its metabolites and thyroid dysfunction. We try to explain the role of the microbiome in the metabolism of thyroid hormones and the impact of thyroid autoimmune diseases. In addition, we raise issues related to the influence of bacterial metabolites, such as short-chain fatty acids or secondary bile acids, in the functioning of the thyroid gland. Last but not least, we explored the interactions between the gut microbiota and therapeutics and supplements typically administered to patients with thyroid diseases.

Gut microbiome and thyroid autoimmunity

Intestinal microbiota gained attention due to its pleiotropic effect on intestinal barrier, nutrients metabolism and on immune system development and functions. Recent evidence pointed out a possible role of an altered gut microbiota composition in the pathogenesis and progression of several autoimmune disorders, occurring at gastrointestinal level or far apart. In thyroid autoimmune disorders, encompassing Hashimoto's thyroiditis, Graves' disease and thyroid-associated orbitopathy, the combined effect of environmental triggers and genetic predisposing background, lead to the loss of self-tolerance and to auto-aggressive damage, involving both cellular and humoral networks of immune system. This review is aimed at assessing the current knowledge about the studies published on the fecal microbiota composition in patients bearing thyroid autoimmune diseases. We further examined the reciprocal interaction between gut microbiota composition and the most used treatments for thyroid disorders.

Study of gut microbiome in Egyptian patients with autoimmune thyroid diseases

BACKGROUND

Hashimoto's thyroiditis (HT) and Graves' disease (GD) are the most prevalent forms of autoimmune thyroid disorders (ATD). A pathogenic link with gut microbial dysbiosis has been described in different autoimmune disorders but not yet fully elucidated in patients with ATD.

AIM OF THE WORK

The present study aimed to elucidate changes in gut microbiome in Egyptian patients with ATD.

PATIENTS AND METHODS

The gut bacterial composition of 20 patients with ATD and 30 age, sex, and BMI-matched healthy subjects as controls was analysed using Quantitative SYBR Green Real-Time PCR technique targeting 16S rRNA of selected bacterial genera and/or species.

RESULTS

Compared with controls; the Firmictus/Bacteroidetes ratio (known to be representative for healthy status) was significantly decreased in patients with ATD (P < .001), without a significant difference between GD and HT patients. Also, the relative abundance of beneficial bacteria associated with the gut barrier and anti-inflammatory state; A. mucinophilia, Bifidobacterium, Lactobacillus, and F. prausnitzii, were decreased in ATD patients. TRAb in GD patients and anti-TPO in HT patients showed a significant positive correlation with Bacteroidetes (P = .001) and (P = .018), respectively.

CONCLUSION

Egyptian patients with ATD show dysbiosis of the gut microbiome that can be related to the pathogenesis of ATD. This hopefully points to the potential therapeutic benefits of manipulating the composition of the gut microbiome in the management or even protection from ATD.

An update on the pathogenesis of Hashimoto's thyroiditis

It is 70 years since Noel Rose embarked on his pioneering studies that lead to the discovery of autoimmune thyroiditis and the elucidation of Hashimoto's thyroiditis. This short review to honour his passing focuses on the developments in our understanding of the causes and pathogenesis of HT over the last five years. Recent genetic studies have reported heritability estimates for HT and associated diseases for the first time, and emphasised the complexity of the genetic factors involved, including monogenic forms of HT. Environmental factors continue to be elucidated, especially as a side effect of drugs which modulate the immune system therapeutically. Regarding pathogenetic mechanisms, multiple cytokine networks have been identified which involve the thyroid cells in a circuit of escalating proinflammatory effects, such as the expression of inflammasome components, and an array of different defects in T regulatory cells may underlie the loss of self-tolerance to thyroid autoantigens. Finally, a number of studies have revealed fresh insights into disease associations with HT which may have both pathological and clinical significance, the most intriguing of which is a possible direct role of the autoimmune process itself in causing some of the persistent symptoms reported by a minority of patients with levothyroxine-treated HT.

Detection of Alterations in the Gut Microbiota and Intestinal Permeability in Patients With Hashimoto Thyroiditis

Hashimoto thyroiditis (HT) is the most common autoimmune disease worldwide, characterized by chronic inflammation and circulating autoantibodies against thyroid peroxidase and thyroglobulin. Patients require hormone replacement with oral levothyroxine, and if untreated, they can develop serious adverse health effects and ultimately death. There is a lot of evidence that the intestinal dysbiosis, bacterial overgrowth, and increased intestinal permeability favor the HT development, and a thyroid–gut axis has been proposed, which seems to impact our entire metabolism. Here, we evaluated alterations in the gut microbiota in Brazilian patients with HT and correlated this data with dietary habits, clinical data, and systemic cytokines and zonulin concentrations. Stool samples from 40 patients with HT and 53 controls were analyzed using real-time PCR, the serum cytokine levels were evaluated by flow cytometry, zonulin concentrations by ELISA, and the dietary habits were recorded by a food frequency questionnaire. We observed a significant increase (p < 0.05) in the Bacteroides species and a decrease in Bifidobacterium in samples of patients with HT. In addition, Lactobacillus species were higher in patients without thyroid hormone replacement, compared with those who use oral levothyroxine. Regarding dietary habits, we demonstrated that there are significant differences in the consumption of vegetables, fruits, animal-derived proteins, dairy products, saturated fats, and carbohydrates between patients and control group, and an inverse correlation between animal-derived protein and Bacteroides genus was detected. The microbiota modulation by diet directly influences the inflammatory profile due to the generated microbiota metabolites and their direct or indirect action on immune cells in the gut mucosa. Although there are no differences in systemic cytokines in our patients with HT, we detected increased zonulin concentrations, suggesting a leaky gut in patients with HT. These findings could help understand the development and progression of HT, while further investigations to clarify the underlying mechanisms of the diet–microbiota–immune system axis are still needed.