The Association of Fecal Microbiota in Ankylosing Spondylitis Cases with C-Reactive Protein and Erythrocyte Sedimentation Rate

Integration of Metabolomics and 16S Ribosomal RNA Sequencing to Elucidate the Pathogenesis of Ankylosing Spondylitis

OBJECTIVE

Despite growing interest in the gut microbiota and blood metabolome in patients with ankylosing spondylitis (AS), its role remains poorly understood. Here, we investigate how microbial and metabolic alterations contribute to AS.

METHODS

Fecal microbiome data from 40 AS patients were compared with those from 40 healthy controls (HCs) using 16S ribosomal RNA (rRNA) gene sequencing. The plasma metabolic profiles were analyzed and integrated with the microbiota data to identify biological characteristics specific to AS.

RESULTS

AS patients showed significant enrichment of specific genera, including Megamonas, Elusimicrobium, Dysgonomonas, Ruminococcus_gauvreauii_group, and unclassified_Prevotellaceae. Pathways with the most differentially expressed metabolites included bile secretion; neomycin, kanamycin, and gentamicin biosynthesis; and arachidonic acid metabolism. Positive correlations between Megamonas and Elusimicrobium and metabolites such as piribedil, l-cystathionine, and crocetin dialdehyde suggested microbial enrichment in AS patients.

CONCLUSIONS

A disrupted gut microbiota and altered metabolites are present in AS patients. Integrating microbiome and metabolomic data reveals significant disruptions in AS patients, improving our understanding of its pathogenesis.

The role of the gastrointestinal microbiome on rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis and reactive arthritis: A systematic review

BACKGROUND

There is an increasing body of literature observing a state of dysbiosis in the gut microbiome in different autoimmune conditions including inflammatory arthritis. It is unknown whether the microbiome can be a biomarker for prognostication purposes or for stratification of treatment strategies. This review aims to evaluate the existing evidence on the association between the microbiome and inflammatory arthritis, including rheumatoid arthritis (RA), psoriatic arthritis (PsA) and ankylosing spondylitis (AS) and reactive arthritis (ReA) population groups.

METHODS

This systematic review was performed based on methods from the Cochrane guidelines and reported based on PRISMA criteria. Studies exploring the microbiome of patients with RA, AS, PsA or ReA compared with controls via 16s rRNA or shotgun sequencing were evaluated. The outcomes of interest include alpha and beta diversity, abundance or depletion of organisms and functional analysis. Literature up to August 2024 was retrieved searching the databases PubMed, Medline, ScienceDirect, Scopus, Web of Science, Cochrane, EMBASE and CINAHL. All references were systematically evaluated by two reviewers. Quality of the studies were evaluated by the Newcastle-Ottawa Scale.

FINDINGS

The review yielded 25,794 search results, of which 53 studies were included for the RA group, 34 studies for the AS group, 6 studies for the PsA group and 2 studies for the ReA group. Reduced diversity has been observed in disease groups and in patients with higher disease activity.

INTERPRETATION

There are limited longitudinal studies on the role of the microbiome in inflammatory arthritis, in particular PsA. Existing cross-sectional studies suggest altered microbiome in disease states compared with controls. Further studies are required to understand the utility of the microbiome as a biomarker to better understand prognosis and tailor treatments.

Inflammatory disease microbiomes share a functional pathogenicity predicted by C-reactive protein

We examine disease-specific and cross-disease functions of the human gut microbiome by colonizing germ-free mice, at risk for inflammatory arthritis, colitis, or neuroinflammation, with over 100 human fecal microbiomes from subjects with rheumatoid arthritis, ankylosing spondylitis, multiple sclerosis, ulcerative colitis, Crohn's disease, or colorectal cancer. We find common inflammatory phenotypes driven by microbiomes from individuals with intestinal inflammation or inflammatory arthritis, as well as distinct functions specific to microbiomes from multiple sclerosis patients. Inflammatory disease in mice colonized with human microbiomes correlated with systemic inflammation, measured by C-reactive protein, in the human donors. These cross-disease patterns of human microbiome pathogenicity mirror features of the inflammatory diseases, including therapeutic targets and the presence or absence of systemic inflammation, suggesting shared and disease-specific mechanisms by which the microbiome is shaped and drives pathogenic inflammatory responses.

Differential Composition and Structure of the Microbiota from Active and Inactive Stages of HLA-B27-associated Uveitis by Paired Fecal Metagenomes

PURPOSE

To compare the diversities and abundances of bacterial taxa in the microbiome of patients with HLA B27-positive acute anterior uveitis (AAU) in the active and inactive phases.

METHODS

An observational descriptive prospective and comparative study was conducted in ten HLA-B27-positive AAU patients (44.6 ± 13.4 years). The microbiome of the stool samples obtained in the active and inactive stages was analyzed by sequencing the V3 region of the 16S rRNA gene.

RESULTS

The differences in the bacteria profile between active and inactive stages in each individual were confirmed (p < 0.0001). Ten OTUs were found exclusively in the active phase of 90% of the individuals, suggesting a proinflammatory association. Blautia OUT_4 and Faecalibacterium OUT_2 abundances showed a direct relationship between abundance and severity of ocular inflammation. Two OTUs were exclusive of the inactive stage, suggesting an anti-inflammatory role.

CONCLUSION

The metagenomic profile of the fecal microbiota differs in the acute phase of the AAU compared to when the inflammation subsides, despite being the same individual and a short time-lapse. AAU is a fertile field for studying the connection between subtle rapid changes in microbiota and their systemic consequences.

Exploring the role of gut microbiome in autoimmune diseases: A comprehensive review

As the industrialized society advances, there has been a gradual increase in the prevalence of autoimmune disorders. A probe into the fundamental causes has disclosed several factors in modern society that have an influence on the gut microbiome. These dramatic shifts in the gut microbiome are likely to be one of the reasons for the disarray in the immune system, and the relationship between the immune system and the gut microbiome emerging as a perennial hot topic of research. This review enumerates the findings from sequencing studies of gut microbiota on seven autoimmune diseases (ADs): Rheumatoid Arthritis (RA), Systemic Lupus Erythematosus (SLE), Ankylosing Spondylitis (AS), Systemic Sclerosis (SSc), Sjögren's Syndrome (SjS), Juvenile Idiopathic Arthritis (JIA), and Behçet's Disease (BD). It aims to identify commonalities in changes in the gut microbiome within the autoimmune disease cohort and characteristics specific to each disease. The dysregulation of the gut microbiome involves a disruption of the internal balance and the balance between the external environment and the host. This dysregulation impacts the host's immune system, potentially playing a role in the development of ADs. Damage to the gut epithelial barrier allows potential pathogens to translocate to the mucosal layer, contacting epithelial cells, disrupting tight junctions, and being recognized by antigen-presenting cells, which triggers an immune response. Primed T-cells assist B-cells in producing antibodies against pathogens; if antigen mimicry occurs, an immune response is generated in extraintestinal organs during immune cell circulation, clinically manifesting as ADs. However, current research is limited; advancements in sequencing technology, large-scale cohort studies, and fecal microbiota transplantation (FMT) research are expected to propel this field to new peaks.

Investigating the causal impact of gut microbiota on arthritis via inflammatory proteins using mendelian randomization

Previous studies have suggested a potential association between the gut microbiota and arthritis. However, the causal links between the gut microbiota and various types of arthritis, as well as the potential mediating role of inflammatory proteins, remain unclear. Mendelian randomization was used to explore the causal relationships between gut microbiota, inflammatory proteins, and various forms of arthritis (osteoarthritis, rheumatoid and psoriatic arthritis, and ankylosing spondylitis [AS]). The inverse variance-weighted method was the primary analytical approach used. Furthermore, we examined the mediating role of inflammatory proteins in the pathway linking the gut microbiota to arthritis. Sensitivity analyses were performed to verify the robustness of the findings, and enrichment analyses were conducted to investigate the biological functions and pathways involved. We identified 11 positive and 14 negative causal effects linking the genetic liability of the gut microbiota to arthritis. Similarly, 9 positive and 8 negative causal effects between inflammatory proteins and arthritis were identified. Notably, an increased abundance of the order Bacillales (odds ratio [OR] = 1.199, 95% confidence interval [CI] = 1.030-1.394, P = 0.019) and higher interleukin-7 levels (OR = 1.322, 95% CI = 1.004-1.741, P = 0.046) significantly elevated the risk of AS. Furthermore, interleukin-7 mediated 13.8% of the effect caused by the order Bacillales, with a mediation effect size of β = 0.025 (95% CI = 0.001-0.064). Sensitivity and supplementary analyses revealed no significant evidence of horizontal pleiotropy or heterogeneity. Overall, our findings demonstrate causal links between the gut microbiota, inflammatory proteins, and four arthritis types, highlighting the gut microbiota as a potential therapeutic target. Crucially, interleukin-7 not only strongly correlated with AS but also partially mediated the effect exerted by the gut microbiota on AS, suggesting that managing the gut microbiota to modulate inflammatory proteins could serve as an effective therapeutic strategy for arthritis.

Inflammatory low back pain-associated malignancies mimicking spondylarthritis

OBJECTIVES

Inflammatory low back pain (IBP) is a typical feature of spondylarthritis (SpA). IBP can be caused by infections, drugs, and different malignancies. Among cancers, hematologic malignancies and solid tumors can cause IBD either paraneoplastically or through metastasis. In this study, we aimed to present the demographic and clinical characteristics of our patients who presented with IBP in the last 10 years and whose final diagnosis was malignancy.

METHODS

Thirty-four patients who presented with inflammatory low back pain in the last 10 years and were diagnosed with malignancy as the final diagnosis were included in the study. Thirty-six patients, diagnosed as axial SpA, with similar age-sex ratio of 1:1 from each center were included as the control group.

RESULTS

Hematologic malignancies were multiple myeloma, acute leukemia, and lymphoma in descending order. Solid tumors were breast cancer, lung cancer, bone tumors, prostate, colon, embryonal carcinoma, and malignancy of unknown primary. In malignancy-related low back pain, the hematologic/solid ratio was similar (18/16), the interval between symptom and diagnosis was shorter, and biomarkers' results such as erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and serum lactate dehydrogenase (LDH) levels were significantly higher than the control group.

CONCLUSION

Malignancy-related low back pain differs from SpA patients with a more severe clinical picture, higher acute phase reactants levels, and higher LDH values. Malignancies must be kept in mind in the differential diagnosis, and in order to validate our findings, the results of larger case series are needed, especially in terms of causative malignancies. Key Points • In malignancy-related inflammatory low back pain, the hematologic/solid ratio was similar, the interval between symptom and diagnosis was shorter, and acute phase reactant levels and LDH levels were significantly higher. • Malignancy-related inflammatory low back pain differs from axial SpA patients with a more severe clinical picture, higher acute phase reactants levels, and higher LDH values. • Malignancies must be kept in mind in the differential diagnosis of axial SpA.

Gut microbiota and risk of ankylosing spondylitis

OBJECTIVE

Observational studies have established a connection between gut microbiota and ankylosing spondylitis (AS) risk; however, whether the observed associations are causal remains unclear. Therefore, we conducted a two-sample Mendelian randomization (MR) analysis to assess the potential causal associations of gut microbiota with AS risk.

METHODS

Instrumental variants of gut microbiota were obtained from the MiBioGen consortium (n = 18,340) and the Dutch Microbiome Project (n = 7738). The FinnGen consortium provided genetic association summary statistics for AS, encompassing 2860 cases and 270,964 controls. We used the inverse-variance weighted (IVW) method as the primary analysis, supplemented with the weighted median method, maximum likelihood-based method, MR pleiotropy residual sum and outlier test, and MR-Egger regression. In addition, we conducted a reverse MR analysis to assess the likelihood of reverse causality.

RESULTS

After the Bonferroni correction, species Bacteroides vulgatus remained statistically significantly associated with AS risk (odds ratio (OR) 1.55, 95% confidence interval (CI) 1.22-1.95, P = 2.55 × 10-4). Suggestive evidence of associations of eleven bacterial traits with AS risk was also observed (P < 0.05 by IVW). Among them, eight were associated with an elevated AS risk (OR 1.37, 95% CI 1.07-1.74, P = 0.011 for phylum Verrucomicrobia; OR 1.31, 95% CI 1.03-1.65, P = 0.026 for class Verrucomicrobiae; OR 1.17, 95% CI 1.01-1.36, P = 0.035 for order Bacillales; OR 1.31, 95% CI 1.03-1.65, P = 0.026 for order Verrucomicrobiales; OR 1.43, 95% CI 1.13-1.82, P = 0.003 for family Alcaligenaceae; OR 1.31, 95% CI 1.03-1.65, P = 0.026 for family Verrucomicrobiaceae; OR 1.31, 95% CI 1.03-1.65, P = 0.026 for genus Akkermansia; OR 1.55, 95% CI 1.19-2.02, P = 0.001 for species Sutterella wadsworthensis). Three traits exhibited a negative association with AS risk (OR 0.68, 95% CI 0.53-0.88, P = 0.003 for genus Dialister; OR 0.84, 95% CI 0.72-0.97, P = 0.020 for genus Howardella; OR 0.75, 95% CI 0.59-0.97, P = 0.026 for genus Oscillospira). Consistent associations were observed when employing alternate MR methods. In the reverse MR, no statistically significant correlations were detected between AS and these bacterial traits.

CONCLUSION

Our results revealed the associations of several gut bacterial traits with AS risk, suggesting a potential causal role of gut microbiota in AS development. Nevertheless, additional research is required to clarify the mechanisms by which these bacteria influence AS risk. Key Points • The association of gut microbiota with AS risk in observational studies is unclear. • This MR analysis revealed associations of 12 gut bacterial traits with AS risk.

Gut microbiota dysbiosis in ankylosing spondylitis: a systematic review and meta-analysis

Background

Ankylosing spondylitis (AS) is a connective tissue disease that primarily affects spinal joints, peripheral joints, and paravertebral soft tissues, leading to joint stiffness and spinal deformity. Growing evidence has implicated gut microbiota in the regulation of AS, though the underlying mechanisms remain poorly understood.

Methods

We conducted a comprehensive search of PubMed, Embase, Web of Science, the Cochrane Library, MEDLINE, Wanfang Data, China Science and Technology Journal Database (VIP), and China National Knowledge Internet (CNKI) databases from the time the databases were created until 30 July 2023. To evaluate changes in α-diversity and the abundance of certain microbiota families in AS, standardized mean difference (SMD) and 95% confidence interval (CI) calculations were made. Meta-analyses were performed using STATA 12.0 and the quality of the literature was assessed by following systematic review guidelines.

Results

This systematic review and meta-analysis included 47 studies, providing insights into the gut microbiota composition in patients with AS compared to healthy controls (HCs). Our findings indicate a significant reduction in gut microbial diversity in patients with AS, as evidenced by a decrease in both richness and evenness. Specifically, the Shannon index showed a moderate decrease (SMD = -0.27, 95% CI: -0.49, -0.04; P < 0.001), suggesting a less diverse microbial ecosystem in patients with AS. The Chao1 index further confirmed this trend, with a larger effect size (SMD = -0.44, 95% CI: -0.80, -0.07; P < 0.001), indicating a lower species richness. The Simpson index also reflected a significant reduction in evenness (SMD = -0.30, 95% CI: -0.53, -0.06; P < 0.001). Additionally, patients with AS who received anti-rheumatic combination treatment exhibited a more pronounced reduction in α-diversity compared to untreated patients, highlighting the potential impact of this treatment on gut microbiota balance. In terms of specific microbial families, we observed a significant decrease in the abundance of Bifidobacterium (SMD = -0.42, 95% CI: -2.37, 1.52; P < 0.001), which is known for its beneficial effects on gut health. Conversely, an increase in the abundance of Bacteroidetes was noted (SMD = 0.42, 95% CI: -0.93, 1.76; P < 0.001), suggesting a possible shift in the gut microbiota composition that may be associated with AS pathophysiology.

Conclusion

Our analysis revealed changes in α-diversity and the relative abundance of specific bacteria in AS. This suggests that targeting the gut microbiota could provide new therapeutic opportunities for treating AS.

Systematic review registration

https://www.crd.york.ac.uk./PROSPERO/, identifier CRD42023450028.

Environmental and Genetic Determinants of Ankylosing Spondylitis

Exposure to heavy metals and lifestyle factors like smoking contribute to the production of free oxygen radicals. This fact, combined with a lowered total antioxidant status, can induce even more damage in the development of ankylosing spondylitis (AS). Despite the fact that some researchers are looking for more genetic factors underlying AS, most studies focus on polymorphisms within the genes encoding the human leukocyte antigen (HLA) system. The biggest challenge is finding the effective treatment of the disease. Genetic factors and the influence of oxidative stress, mineral metabolism disorders, microbiota, and tobacco smoking seem to be of great importance for the development of AS. The data contained in this review constitute valuable information and encourage the initiation and development of research in this area, showing connections between inflammatory disorders leading to the pathogenesis of AS and selected environmental and genetic factors.

The gut microbiome and HLA-B27-associated anterior uveitis: a case-control study

BACKGROUND

The human gut microbiome (GM) is involved in inflammation and immune response regulation. Dysbiosis, an imbalance in this ecosystem, facilitates pathogenic invasion, disrupts immune equilibrium, and potentially triggers diseases including various human leucocyte antigen (HLA)-B27-associated autoinflammatory and autoimmune diseases such as inflammatory bowel disease (IBD) and spondyloarthropathy (SpA). This study assesses compositional and functional alterations of the GM in patients with HLA-B27-associated non-infectious anterior uveitis (AU) compared to healthy controls.

METHODS

The gut metagenomes of 20 patients with HLA-B27-associated non-infectious AU, 21 age- and sex-matched HLA-B27-negative controls, and 6 HLA-B27-positive healthy controls without a history of AU were sequenced using the Illumina NovaSeq 6000 platform for whole metagenome shotgun sequencing. To identify taxonomic and functional features with significantly different relative abundances between groups and to identify associations with clinical metadata, the multivariate association by linear models (MaAsLin) R package was applied.

RESULTS

Significantly higher levels of the Eubacterium ramulus species were found in HLA-B27-negative controls (p = 0.0085, Mann-Whitney U-test). No significant differences in microbial composition were observed at all other taxonomic levels. Functionally, the lipid IVA biosynthesis pathway was upregulated in patients (p < 0.0001, Mann-Whitney U-test). A subgroup analysis comparing patients with an active non-infectious AU to their age- and sex-matched HLA-B27-negative controls, showed an increase of the species Phocaeicola vulgatus in active AU (p = 0.0530, Mann-Whitney U-test). An additional analysis comparing AU patients to age- and sex-matched HLA-B27-positive controls, showed an increase of the species Bacteroides caccae in controls (p = 0.0022, Mann-Whitney U-test).

CONCLUSION

In our cohort, non-infectious AU development is associated with compositional and functional alterations of the GM. Further research is needed to assess the causality of these associations, offering potentially novel therapeutic strategies.

6-formylindolo[3, 2-b]carbazole alters gut microbiota and prevents the progression of ankylosing spondylitis in mice

Ankylosing spondylitis (AS), is known as a chronic inflammatory autoimmune disease, there is evidence to suggest that gut microbiota disorders may be related to the occurrence and development of AS. Studies have shown that 6-formylindolo[3, 2-b]carbazole (FICZ) has the ability to modulate intestinal homeostasis and inhibit inflammatory responses. The purpose of this work is to evaluate the protective role of FICZ in treating AS and elucidate potential mechanisms. FICZ was administered to the proteoglycan (PG)-induced AS mice for 7 consecutive weeks. The effects of FICZ on AS mice were evaluated by the disease severity, intestinal histopathology, proinflammatory cytokine levels, and intestinal mucosal barrier function. The gut microbiota compositions were profiled through 16S rDNA high-throughput sequencing. We found that FICZ significantly reduced the severity of AS and resulted in the downregulating of TNF-α and IL-17A inflammatory cytokines. Moreover, FICZ ameliorated pathological changes in the ileal and improved intestinal mucosal barrier function. Furthermore, FICZ altered the composition of the gut microbiota by increasing the Bacteroidetes/Firmicutes phylum ratio and enriched the genes related to "glycan biosynthesis and metabolism", thus reversing the process of AS. In conclusion, FICZ suppressed the progression of AS and altered gut microbiota in AS mice, which provided new insight into AS therapy strategy.

The causality between gut microbiota and ankylosing spondylitis: Insights from a bidirectional two-sample Mendelian randomization analysis

BACKGROUND

The association between gut microbiota and ankylosing spondylitis (AS) has been reported in the literature; however, whether the two are correlative is unclear.

METHODS

Single nucleotide polymorphisms associated with the gut microbiome composition and AS (968 AS cases and 336 191 controls) were obtained from published genome-wide association studies in this two-sample Mendelian randomization (MR) study. The causal relationship between gut microbiota and AS was estimated using the inverse-variance weighted method, and the robustness of our findings was confirmed through a comprehensive series of sensitivity analyses.

RESULTS

Anaerotruncus (OR = 0.9984, 95% CI, 0.9968-0.9999, p = .0405) and Ruminococcaceae UCG002 (OR = 0.9989, 95% CI, 0.9979-0.9999, p = .0375) were protective against AS. Defluviitaleaceae (OR = 1.0015, 95% CI, 1.0005-1.0025, p = .0048), Butyricicoccus (OR = 1.0016, 95% CI, 1.0001-1.0032, p = .0429), Coprococcus 3 (OR = 1.0016, 95% CI, 1.0000-1.0032, p = .0463), and Defluviitaleaceae UCG011 (OR = 1.0016, 95% CI, 1.0005-1.0027, p = .0041) exhibited significant positive correlations with heightened susceptibility to AS. Reverse MR revealed that AS does not affect the gut microbial composition.

CONCLUSION

Our study has established a genetically-based causal relationship between gut microbiota and AS. This finding suggests that we may be able to target and regulate specific bacterial groups in the gut to prevent and treat AS.

Discovery of fecal microbial signatures in patients with ankylosing spondylitis

Objectives

This study aimed to investigate the characteristics of the gut microbiota in Chinese patients with ankylosing spondylitis (AS) and healthy controls in Quanzhou aiming to explore the correlation between microbiome changes and AS activities.

Patients and methods

In this study, high-throughput sequencing of the gene of 16S ribosomal RNA (16S rRNA) in fecal samples from 40 AS patients and 40 healthy controls, for a total of 80 participants (70 males, 10 females; mean age 33.7±10.7 years; range, 15 to 58 years), was conducted between January 2018 and January 2019. Alpha and beta diversity were analyzed using the QIIME (Quantitative Insights Into Microbial Ecology) software, and differences were analyzed using Student's t-test, linear discriminant analysis coupled with effect size and Metastats. Finally, a correlation network was constructed using Pearson's analysis.

Results

The alpha index values of the AS group were not significantly different from those of the control group. At the genus level, eight genera, Ruminiclostridium_9, Fusicatenibacter, Adlercreutzia, CAG-56, Intestinimonas, Lachnospira, Bacteroides, and Pseudoflavonifractor, were significantly enriched in patients with AS, whereas the abundance of uncultured_bacterium_f_Saccharimonadaceae, Prevotella_7, uncultured_bacterium_f_ Enterobacteriaceae, Cronobacter, Prevotellaceae_NK3B31_group, and Weissella were significantly decreased in patients with AS. In addition, diseaserelated gut microbial communities were detected in patients with AS.

Conclusion

We found differences in the gut microbiome between the patients with AS and controls and identified potential disease activity-related bacterial communities.

Case report: Fecal microbiota transplantation in refractory ankylosing spondylitis

Ankylosing spondylitis (AS) is the prototype of a group of systemic inflammatory diseases referred to as spondyloarthritis. Comorbid inflammatory bowel disease and changed gut microbiota in AS have attracted attention to the influence of gut-joint axis and encouraged treating AS by targeting gut microbiota. Here we first reported a patient with refractory AS and comorbid ulcerative colitis (UC) who underwent three fecal microbiota transplantations (FMTs). Inadequate response to conventional treatments including tumor necrosis factor inhibitors impelled FMT as alternative therapy. Notable improvements in AS and UC accompanied with changed fecal microbiota were recorded at 1 week post-FMT1. Further recovery was found after the other two FMTs, and a roughly stable status was maintained in the follow-up period. More studies are needed to validate the effectiveness of FMT in AS and its mechanisms.

Joint together: The etiology and pathogenesis of ankylosing spondylitis

Spondyloarthritis (SpA) refers to a group of diseases with inflammation in joints and spines. In this family, ankylosing spondylitis (AS) is a rare but classic form that mainly involves the spine and sacroiliac joint, leading to the loss of flexibility and fusion of the spine. Compared to other diseases in SpA, AS has a very distinct hereditary disposition and pattern of involvement, and several hypotheses about its etiopathogenesis have been proposed. In spite of significant advances made in Th17 dynamics and AS treatment, the underlying mechanism remains concealed. To this end, we covered several topics, including the nature of the immune response, the microenvironment in the articulation that is behind the disease's progression, and the split between the hypotheses and the evidence on how the intestine affects arthritis. In this review, we describe the current findings of AS and SpA, with the aim of providing an integrated view of the initiation of inflammation and the development of the disease.

Role of the microbiome and its metabolites in ankylosing spondylitis

Ankylosing spondylitis (AS), a chronic condition that commonly influences the spine and sacroiliac joints, usually progresses to stiffness and progressive functional limitation. Its fundamental etiology and pathogenesis are likely multifactorial and remain elusive. As environmental factors, gut microbiota performs critical functions in the pathogenesis of AS through various mechanisms, including interacting with genes, enhancing intestinal permeability, activating the gut mucosa immune system, and affecting the intestinal microbiota metabolites. This review provides an overview of recent advances in investigating gut microbiota in AS pathogenesis and discusses potential methods for future therapeutic intervention.

Microbiota-assisted therapy for systemic inflammatory arthritis: advances and mechanistic insights

Research on the influence of gut microbiota on systemic inflammatory arthritis has exploded in the past decade. Gut microbiota changes may be a crucial regulatory component in systemic inflammatory arthritis. As a result of advancements in the field, microbiota-assisted therapy has evolved, but this discipline is still in its infancy. Consequently, we review the limitations of current systemic inflammatory arthritis treatment, analyze the connection between the microbiota and arthritis, and summarize the research progress of microbiota regulating systemic inflammatory arthritis and the further development aspects of microbiota-assisted therapy. Finally, the partial mechanisms of microbiota-assisted therapy of systemic inflammatory arthritis are being discussed. In general, this review summarizes the current progress, challenges, and prospects of microbiota-assisted therapy for systemic inflammatory arthritis and points out the direction for the development of microbiota-assisted therapy in the future.

Gut microbiota changes in patients with spondyloarthritis: A systematic review

OBJECTIVE

Gut microbiota has been proposed as a pivotal role in the progression of Spondyloarthritis (SpA), however diverse results remain to be synthesized. We performed a systematic review to collect evidence on the characteristic of the gut microbiota in patients with SpA, as compared to controls.

METHODS

We systematically searched MEDLINE, EMBASE, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials databases, through June 1, 2021 for studies that compared gut microbiota of cases with SpA versus healthy controls.

RESULTS

Of 3756 records identified, 28 studies from 23 articles were included in the analysis. Results of β-diversity showed SpA patients hold a significantly different microbial composition compared with controls. Several taxa-level differences of gut microbiota between SpA (and its subtypes) cases and controls were identified. Fourteen studies including only patients with ankylosing spondylitis (AS) reported increased amounts of Actinobacteria, Dialister, Streptococcus, and Clostridium bolteae, and decreased amounts of Bacteroidales and Parasutterella in AS cases versus controls in ≥ 3 studies. Dialister invisus was increased in axial-SpA cases versus controls in 3 studies. Bacteroides fragilis was increased in enthesitis-related arthritis (ERA) cases versus controls in 2 studies. For all SpA studies, Proteobacteria, Enterobacteriaceae, and Bacteroidaceae were increased, whereas Bacteroidetes, Bacteroidales, and Akkermansia were decreased in cases versus controls in ≥ 3 studies. Over 40% of the studies showed comparable data of both sex and age between cases and controls.

CONCLUSION

The microbial characteristics of SpA summarized in the systematic review laid the groundwork for evidence-based microbial treatment. The microbial variance among subtypes of SpA remains to be explored. Further studies are needed to elucidate how the altered microbiota participate in the pathogenesis of SpA.

Nontargeted Metabolomic Analysis of Plasma Metabolite Changes in Patients with Adolescent Idiopathic Scoliosis

Objective

Adolescent idiopathic scoliosis (AIS) is a relatively common spinal rotation deformity, and the pathogenesis of AIS is accompanied by metabolic dysfunction and changes in biochemical factors. In this study, plasma metabolite changes in AIS patients were analyzed based on nontargeted metabolomics to provide new insights for clarifying functional metabolic abnormalities in AIS patients.

Methods

Clinical indexes and blood samples were collected from 12 healthy subjects and 16 AIS patients. Metabolomics was used to analyze the changes in metabolites in plasma samples. The correlation between plasma metabolites and clinical indexes was analyzed by the Spearman rank correlation coefficient.

Results

Analysis of clinical data showed that the body weight, body mass index (BMI), and bone mineral density (BMD) index of the AIS group significantly decreased, while the blood phosphorus and Cobb angles increased significantly. Metabolomic analysis showed significant changes in 72 differential metabolites in the plasma of the AIS group, mainly including organooxygen compounds, carboxylic acids and derivatives, fatty acyls, steroids and steroid derivatives, and keto acids and derivatives. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway showed that arginine biosynthesis, D-glutamine and D-glutamate metabolism, alanine, aspartate and glutamate metabolism, and citrate cycle (TCA cycle) were significantly enriched in the AIS and healthy groups. Spearman rank correlation coefficient analysis showed that the plasma metabolites C00026 (oxoglutarate), C00062 (L-arginine, arginine), C01042 (N-acetylaspartate), and C00158 (citrate) were significantly correlated with clinical indexes in AIS patients. In the healthy group, the plasma metabolites C00122 (fumarate), C00025 (glutamate and L-glutamic acid) and C00149 (malate, L-malic acid) were significantly correlated with clinical indexes, while C00624 (N-acetylglutamate) was not significantly correlated with the clinical indexes.

Conclusion

The occurrence of AIS led to changes in clinical indexes and plasma metabolites. Plasma biomarkers and functional metabolic pathways were correlated with clinical indexes, which might provide new insights for the diagnosis and treatment of AIS.