Study of gut microbiome in Egyptian patients with autoimmune thyroid diseases

Bacteroidaceae, Bacteroides, and Veillonella: emerging protectors against Graves' disease

Background

Graves' disease (GD) is the most common cause of hyperthyroidism, and its pathogenesis remains incompletely elucidated. Numerous studies have implicated the gut microbiota in the development of thyroid disorders. This study employs Mendelian randomization analysis to investigate the characteristics of gut microbiota in GD patients, aiming to offer novel insights into the etiology and treatment of Graves' disease.

Methods

Two-sample Mendelian randomization (MR) analysis was employed to assess the causal relationship between Graves' disease and the gut microbiota composition. Gut microbiota data were sourced from the international consortium MiBioGen, while Graves' disease data were obtained from FINNGEN. Eligible single nucleotide polymorphisms (SNPs) were selected as instrumental variables. Multiple analysis methods, including inverse variance-weighted (IVW), MR-Egger regression, weighted median, weighted mode, and MR-RAPS, were utilized. Sensitivity analyses were conducted employing MR-Egger intercept test, Cochran's Q test, and leave-one-out analysis as quality control measures.

Results

The Mendelian randomization study conducted in a European population revealed a decreased risk of Graves' disease associated with Bacteroidaceae (Odds ratio (OR) [95% confidence interval (CI)]: 0.89 [0.89 ~ 0.90], adjusted P value: <0.001), Bacteroides (OR: [95% CI]: 0.555 [0.437 ~ 0.706], adjusted P value: <0.001), and Veillonella (OR [95% CI]: 0.632 [0.492 ~ 0.811], adjusted P value: 0.016). No significant evidence of heterogeneity, or horizontal pleiotropy was detected. Furthermore, the preliminary MR analysis identified 13 bacterial species including Eubacterium brachy group and Family XIII AD3011 group, exhibiting significant associations with Graves' disease onset, suggesting potential causal effects.

Conclusion

A causal relationship exists between gut microbiota and Graves' disease. Bacteroidaceae, Bacteroides, and Veillonella emerge as protective factors against Graves' disease development. Prospective probiotic supplementation may offer a novel avenue for adjunctive treatment in the management of Graves' disease in the future.

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.

Intestinal permeability is associated with aggravated inflammation and myofibroblast accumulation in Graves' orbitopathy: the MicroGO study

Background

Graves' disease (GD) and Graves' orbitopathy (GO) result from ongoing stimulation of the TSH receptor due to autoantibodies acting as persistent agonists. Orbital pre-adipocytes and fibroblasts also express the TSH receptor, resulting in expanded retro-orbital tissue and causing exophthalmos and limited eye movement. Recent studies have shown that GD/GO patients have a disturbed gut microbiome composition, which has been associated with increased intestinal permeability. This study hypothesizes that enhanced intestinal permeability may aggravate orbital inflammation and, thus, increase myofibroblast differentiation and the degree of fibrosis.

Methods

Two distinct cohorts of GO patients were studied, one of which was a unique cohort consisting of blood, fecal, and retro-orbital tissue samples. Intestinal permeability was assessed by measuring serum lipopolysaccharide-binding protein (LBP), zonulin, TLR5, and TLR9 ligands. The influx of macrophages and accumulation of T-cells and myofibroblast were quantified in orbital connective tissue. The NanoString immune-oncology RNA targets panel was used to determine the transcriptional profile of active fibrotic areas within orbital sections.

Results

GO patients displayed significantly higher LBP serum concentrations than healthy controls. Within the MicroGO cohort, patients with high serum LBP levels also showed higher levels of zonulin and TLR5 and TLR9 ligands in their circulation. The increased intestinal permeability was accompanied by augmented expression of genes marking immune cell infiltration and encoding key proteins for immune cell adhesion, antigen presentation, and cytokine signaling in the orbital tissue. Macrophage influx was positively linked to the extent of T cell influx and fibroblast activation within GO-affected orbital tissues. Moreover, serum LBP levels significantly correlated with the abundance of specific Gram-negative gut bacteria, linking the gut to local orbital inflammation.

Conclusion

These results indicate that GO patients have enhanced intestinal permeability. The subsequent translocation of bacterial compounds to the systemic circulation may aggravate inflammatory processes within the orbital tissue and, as a consequence, augment the proportion of activated myofibroblasts, which actively secrete extracellular matrix leading to retro-orbital tissue expansion. These findings warrant further exploration to assess the correlation between specific inflammatory pathways in the orbital tissue and the gut microbiota composition and may pave the way for new microbiota-targeting therapies.

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.

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.

Study of the gut microbiome in Egyptian patients with Parkinson's Disease

BACKGROUND

Recently, an important relationship between Parkinson's disease and the gut microbiota, through the brain-gut axis interactions, has been established. Previous studies have declared that alterations in the gut microbiota have a great impact on the pathogenesis and clinical picture of Parkinson's disease (PD). The present study aimed to identify the gut microbiome that is likely related to Parkinson's disease as well as their possible relation to clinical phenotypes.

METHODS

Thirty patients with Parkinson's disease, who presented to the Parkinson's disease Neurology Clinic of Alexandria University Hospital were enrolled in our study. A cross-matching control group of 35 healthy subjects of similar age and sex were included. Stool specimens were taken from each. Quantitative SYBR Green Real-Time PCR was done for the identification and quantitation of selected bacterial phyla, genera and/or species.

RESULTS

There was a significant increase in Bacteroides and a significant decrease of Firmicutes and Firmicutes / Bacteroidetes ratio and Bifidobacteria in PD patients. Although Prevotella was decreased among PD patients relative to the healthy control, the difference was not statistically significant. Comparing the PD clinical phenotypes with the control group, the Mixed phenotype had significantly higher Bacteroides, Tremors predominant had lower Firmicutes and Firmicutes / Bacteroidetes ratio, and both tremors and postural instability and gait disability (PIGD) phenotypes had lower Bifidobacteria. However, there was no statistically significant difference between these phenotypes. Furthermore, when comparing tremors and non-tremors predominant phenotypes; Lactobacilli showed a significant decrease in non-tremors predominant phenotypes.

CONCLUSIONS

The current study showed evidence of changes in the gut microbiome of Parkinson's disease patients compared to the healthy controls. These observations may highlight the importance of the identification of microbiome and specific bacterial changes that can be targeted for the treatment of Parkinson's disease.

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.

Study of the gut microbiome as a novel target for prevention of hospital-associated infections in intensive care unit patients

BACKGROUND

Hospital-acquired infections (HAIs) are increasing due to the spread of multi-drugresistant organisms. Gut dysbiosis in an intensive care unit (ICU) patients at admission showed an altered abundance of some bacterial genera associated with the occurrence of HAIs and mortality. In the present study, we investigated the pattern of the gut microbiome in ICU patients at admission to correlate it with the development of HAIs during ICU stay.

METHODS

Twenty patients admitted to an ICU with a cross-matched control group of 30 healthy subjects of matched age and sex. Quantitative SYBR green real-time polymerase chain reaction was done for the identification and quantitation of selected bacteria.

RESULTS

Out of those twenty patients, 35% developed ventilator-associated pneumonia during their ICU stay. Gut microbiome analysis showed a significant decrease in Firmicutes and Firmicutes to Bacteroidetes ratio in ICU patients in comparison to the control and in patients who developed HAIs in comparison to the control group and patients who did not develop HAIs. There was a statistically significant increase in Bacteroides in comparison to the control group. There was a statistically significant decrease in Bifidobacterium and Faecalibacterium prausnitzii and an increase in Lactobacilli in comparison to the control group with a negative correlation between Acute Physiology and Chronic Health Evaluation (APACHE) II score and Firmicutes to Bacteroidetes and Prevotella to Bacteroides ratios.

CONCLUSIONS

Gut dysbiosis of patients at the time of admission highlights the importance of identification of the microbiome of patients admitted to the ICU as a target for preventing of HAIs.

A cause-effect relationship between Graves' disease and the gut microbiome contributes to the thyroid-gut axis: A bidirectional two-sample Mendelian randomization study

Background

An association between Graves' disease (GD) and the gut microbiome has been identified, but the causal effect between them remains unclear.

Methods

Bidirectional two-sample Mendelian randomization (MR) analysis was used to detect the causal effect between GD and the gut microbiome. Gut microbiome data were derived from samples from a range of different ethnicities (18,340 samples) and data on GD were obtained from samples of Asian ethnicity (212,453 samples). Single nucleotide polymorphisms (SNPs) were selected as instrumental variables according to different criteria. They were used to evaluate the causal effect between exposures and outcomes through inverse-variance weighting (IVW), weighted median, weighted mode, MR-Egger, and simple mode methods. F-statistics and sensitivity analyses were performed to evaluate bias and reliability.

Results

In total, 1,560 instrumental variables were extracted from the gut microbiome data (p< 1 × 10⁵). The classes Deltaproteobacteria [odds ratio (OR) = 3.603] and Mollicutes, as well as the genera Ruminococcus torques group, Oxalobacter, and Ruminococcaceae UCG 011 were identified as risk factors for GD. The family Peptococcaceae and the genus Anaerostipes (OR = 0.489) were protective factors for GD. In addition, 13 instrumental variables were extracted from GD (p< 1 × 10^-8), causing one family and eight genera to be regulated. The genus Clostridium innocuum group (p = 0.024, OR = 0.918) and Anaerofilum (p = 0.049, OR = 1.584) had the greatest probability of being regulated. Significant bias, heterogeneity, and horizontal pleiotropy were not detected.

Conclusion

A causal effect relationship exists between GD and the gut microbiome, demonstrating regulatory activity and interactions, and thus providing evidence supporting the involvement of a thyroid-gut axis.

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.

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.

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.

Compositional variation of the human fecal microbiome in relation to azo-reducing activity: a pilot study

Background

Through an arsenal of microbial enzymes, the gut microbiota considerably contributes to human metabolic processes, affecting nutrients, drugs, and environmental poisons. Azoreductases are a predominant group of microbiota-derived enzymes involved in xenobiotic metabolism and drug activation, but little is known about how compositional changes in the gut microbiota correlate with its azo-reducing activity.

Results

To this end, we used high-throughput 16S rRNA amplicon sequencing, with Illumina MiSeq, to determine the microbial community composition of stool samples from 16 adults with different azo-reducing activity. High azo-reducing activity positively correlated with the relative abundance of phylum Firmicutes (especially genera Streptococcus and Coprococcus) but negatively with phylum Bacteroidetes (especially genus Bacteroides). Typical variations in the Firmicutes-to-Bacteroidetes and Prevotella-to-Bacteroides ratios were observed among samples. Multivariate analysis of the relative abundance of key microbial taxa and other diversity parameters confirmed the Firmicutes proportion as a major variable differentiating high and non-azo-reducers, while Bacteroidetes relative abundance was correlated with azo-reduction, sex, and BMI.

Conclusions

This pilot study showed that stool samples with higher azo-reducing activity were enriched in Firmicutes but with relatively fewer Bacteroidetes. More samples and studies from different geographical areas are needed to bolster this conclusion. Better characterization of different azoreductase-producing gut microbes will increase our knowledge about the fate and differential human responses to azodye-containing drugs or orally consumed chemicals, thus contributing to efforts towards implementing microbiome testing in precision medicine and toxicology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-021-00454-0.

Association Between Gut Microbiota and Autoimmune Thyroid Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Autoimmune thyroid disease (AITD) is characterized by thyroid dysfunction and deficits in the autoimmune system. Growing attention has been paid toward the field of gut microbiota over the last few decades. Several recent studies have found that gut microbiota composition in patients with AITD has altered, but no studies have conducted systematic reviews on the association between gut microbiota and ATID.

METHODS

We searched PubMed, Web of Science, Embase, and Cochrane databases without language restrictions and conducted a systematic review and meta-analysis of eight studies, including 196 patients with AITD.

RESULTS

The meta-analysis showed that the alpha diversity and abundance of certain gut microbiota were changed in patients with AITD compared to the controls. Chao1,the index of the microflora richness, was increased in the Hashimoto's thyroiditis group compared to controls (SMD, 0.68, 95%CI: 0.16 to 1.20), while it was decreased in the Graves' disease group (SMD, -0.87, 95%CI: -1.46 to -0.28). In addition, we found that some beneficial bacteria like Bifidobacterium and Lactobacillus were decreased in the AITD group, and harmful microbiota like Bacteroides fragilis was significantly increased compared with the controls. Furthermore, the percentage of relevant abundance of other commensal bacteria such as Bacteroidetes, Bacteroides, and Lachnospiraceae was increased compared with the controls.

CONCLUSIONS

This meta-analysis indicates an association between AITD and alteration of microbiota composition at the family, genus, and species levels.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, identifier CRD42021251557.