Gut microbiota changes in patients with spondyloarthritis: A systematic review

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 the intestinal MiCrobiome in InflammATory bowel disease-AssocIated SpONdylarthritis (LOCATION-IBD)

Background

Inflammatory Bowel Disease (IBD)-associated arthritis is a frequent and potentially debilitating complication of IBD, that can affect those with or without active intestinal disease, and is often difficult to treat. The microbiome is known to play a role in IBD development and has been shown to be associated with inflammatory arthritis without concomitant IBD, but its role in IBD-associated arthritis is still unexplored. Further, disease localization is associated with development of IBD-associated arthritis, and stool compositional profiles are predictive of disease localization, yet mucosal location-specific microbiomes have not been well characterized. To address this gap in understanding, we designed a study (LOCATION-IBD) to characterize the mucosa-associated intestinal microbiome and metabolome in IBD-associated arthritis.

Methods

Adults with an established diagnosis of IBD undergoing clinical colonoscopy between May of 2021 and February of 2023 were invited to participate in this study; those interested in participation who met inclusion criteria were enrolled. Prior to enrollment, participants were stratified into those with or without IBD-associated arthritis. All participants were interviewed and had clinical and demographic data collected, and 97.8% completed clinical colonoscopy with biopsy collection.

Results and conclusion

A total of 182 participants, 53 with confirmed IBD-associated arthritis, were enrolled in this study, resulting in 1151 biopsies obtained for microbiome and metabolome analysis (median 6, mean 6.3 per participant). Clinical and demographic data obtained from the study population will be analyzed with microbiome and metabolome data obtained from biopsies, with the goal of better understanding the mechanisms underpinning the host-microbiome relationship associated the development of IBD-associated arthritis.

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.

Causal association of gut microbiota on spondyloarthritis and its subtypes: a Mendelian randomization analysis

Background

Despite establishing an association between gut microbiota and spondyloarthritis (SpA) subtypes, the causal relationship between them remains unclear.

Methods

Gut microbiota data were obtained from the MiBioGen collaboration, and SpA genome-wide association study (GWAS) summary data were obtained from the FinnGen collaboration. We conducted a two-sample Mendelian randomization (MR) analysis using the inverse-variance-weighted method supplemented with four additional MR methods (MR-Egger, weighted median, simple mode, and weighted mode). Pleiotropy and heterogeneity were also assessed. Reverse MR analysis was used to detect reverse causal relationships.

Results

We identified 23 causal links between specific gut microbiota taxa and SpA levels. Of these, 22 displayed nominal causal associations, and only one demonstrated a robust causal connection. Actinobacteria id.419 increased the risk of ankylosing spondylitis (AS) (odds ratio (OR) = 1.86 (95% confidence interval (CI): 1.29-2.69); p = 8.63E-04). The family Rikenellaceae id.967 was associated with a reduced risk of both AS (OR = 0.66 (95% CI: 0.47-0.93); p = 1.81E-02) and psoriatic arthritis (OR = 0.70 (95% CI: 0.50-0.97); p = 3.00E-02). Bacillales id.1674 increased the risk of AS (OR = 1.23 (95% CI: 1.00-1.51); p = 4.94E-02) and decreased the risk of enteropathic arthritis (OR = 0.56 (95% CI: 0.35-0.88); p = 1.14E-02). Directional pleiotropy, or heterogeneity, was not observed. No reverse causal associations were observed between the diseases and the gut microbiota.

Conclusion

Our MR analysis suggested a genetic-level causal relationship between specific gut microbiota and SpA, providing insights into the underlying mechanisms behind SpA development mediated by gut microbiota.

Beyond the horizon: Innovations and future directions in axial-spondyloarthritis

Axial spondyloarthritis (axSpA) is a chronic inflammatory disease of the spine and sacroiliac joints. This review discusses recent advances across multiple scientific fields that promise to transform axSpA management. Traditionally, axSpA was considered an immune-mediated disease driven by human leukocyte antigen B27 (HLA-B27), interleukin (IL)-23/IL-17 signaling, biomechanics, and dysbiosis. Diagnosis relies on clinical features, laboratory tests, and imaging, particularly magnetic resonance imaging (MRI) nowadays. Management includes exercise, lifestyle changes, non-steroidal anti-inflammatory drugs and if this is not sufficient to achieve disease control also biological and targeted-synthetic disease modifying anti-rheumatic drugs. Beyond long-recognized genetic risks like HLA-B27, high-throughput sequencing has revealed intricate gene-environment interactions influencing dysbiosis, immune dysfunction, and aberrant bone remodeling. Elucidating these mechanisms promises screening approaches to enable early intervention. Advanced imaging is revolutionizing the assessment of axSpA's hallmark: sacroiliac bone-marrow edema indicating inflammation. Novel magnetic resonance imaging (MRI) techniques sensitively quantify disease activity, while machine learning automates complex analysis to improve diagnostic accuracy and monitoring. Hybrid imaging like synthetic MRI/computed tomography (CT) visualizes structural damage with new clarity. Meanwhile, microbiome analysis has uncovered gut ecosystem alterations that may initiate joint inflammation through HLA-B27 misfolding or immune subversion. Correcting dysbiosis represents an enticing treatment target. Moving forward, emerging techniques must augment patient care. Incorporating patient perspectives will be key to ensure innovations like genetics, microbiome, and imaging biomarkers translate into improved mobility, reduced pain, and increased quality of life. By integrating cutting-edge, multidisciplinary science with patients' lived experience, researchers can unlock the full potential of new technologies to deliver transformative outcomes. The future is bright for precision diagnosis, tightly controlled treatment, and even prevention of axSpA.

Pathophysiology and immunolgical basis of axial spondyloarthritis

Over the recent years the wider availability and application of state-of-the-art immunological technologies greatly advanced the insight into the mechanisms that play an important role in axial spondyloarthritis (axSpA) pathophysiology. This increased understanding has facilitated the development of novel treatments that target disease relevant pathways, hereby improving outcome for axSpA patients. In axSpA pathophysiology genetic and environmental factors as well as immune activation by mechanical or bacterial stress resulting in a chronic inflammatory response have a central role. The TNF and IL-23/IL-17 immune pathways play a pivotal role in these disease mechanisms. This review provides an outline of the immunological basis of axSpA with a focus on key genetic risk factors and their link to activation of the pathological immune response, as well as on the role of the gut and entheses in the initiation of inflammation with subsequent new bone formation in axSpA.

Association of ADRB2 gene polymorphisms and intestinal microbiota in Chinese Han adolescents

Gut microbiota are closely related to health, and the β2-adrenergic receptor (ADRB2) gene is associated with gastrointestinal diseases. However, little is known about the relationship between ADRB2 gene polymorphisms and intestinal microbiota. In the present study, we aimed to explore the relationship between ADRB2 gene polymorphisms and gut microbiota in Chinese Han adolescents. Data analysis showed that the relative abundance, PICRUSt function prediction, and Chao1 and ACE indices of gut microbiota were significantly different between males and females (P < 0.05). The rs1042711 was positively associated with the relative abundance of Actinobacteria, Coriobacteriia, Bifidobacteriales, Erysipelotrichi, and Erysipelotrichales. The rs12654778 was negatively associated with Bacilli, Lactobacillales, Bacteroidaceae, and Bacteroides. rs1042713 was positively associated with Lactobacillales and Bifidobacteriales. The rs1042717 was positively associated with Bifidobacteriales and negatively associated with Veillonellaceae. The rs1042719 was negatively associated with Erysipelotrichi and Erysipelotrichales and positively associated with Erysipelotrichi, Erysipelotrichales, Bifidobacteriales, and Ruminococcaceae in females. The rs1801704 was positively associated with Erysipelotrichi, Erysipelotrichales, Bifidobacteriales, Actinobacteria, Coriobacteriia, and Bifidobacteriales. The rs2053044 was positively associated with Ruminococcaceae, Dialister, Firmicutes, Clostridia, Clostridiales, Bifidobacteriales, and Faecalibacterium and negatively associated with Bacilli, Lactobacillales, Lachnospiraceae, and Porphyromonadaceae (P < 0.05). These results suggested that the relative abundance, diversity, and PICRUSt function predictions of male and female gut microbiomes differ significantly and that ADRB2 gene polymorphisms were associated with gut microbiome abundance in Chinese Han adolescents.

Adiposity is associated with expansion of the genus Dialister in rheumatoid arthritis patients

OBJECTIVE

To analyze the intestinal microbiota of patients with rheumatoid arthritis (RA) and obesity and a higher percentage of fatty tissue.

METHODS

Nested case-control study of 80 RA patients and 80 age and sex-matched controls. Obesity was defined as a body mass index ≥ 30, and body composition using dual-energy x-ray absorptiometry. The gut microbiota was analyzed using 16 S rRNA gene sequencing; bioinformatics analysis was performed using QIIME2 and PICRUSt. Other variables included averaged 28-joint Disease Activity Score (DAS28-ESR), cytokines and adipokines. Two multivariate were constructed with obesity and fat mass index (FMI).

RESULTS

Obesity was more frequent in RA patients than in controls (36.3 % vs 25.1 %; p = 0.026), as was a higher FMI value (mean [SE]=11.6 [3.9] vs 10.2 [3.9]; p = 0.032). Alpha and beta diversity analysis revealed differences in gut microbiota between RA patients with and without obesity. Dialister and Odoribacter were more abundant in RA patients with obesity than in RA patients without obesity, while the genus Clostridium was more abundant in RA patients without obesity. The factors associated with obesity in RA patients were age (OR [95 % CI], 1.09 [1.02-1.17]), mean DAS28-ESR (OR [95 % CI], 1.46 [1.12-1.67]), leptin levels (OR [95 % CI], 1.06 [1.01-1.10]), the genus Dialister (OR [95 % CI], 1.03 [1.01-1.07]), and the genus Clostridium (OR [95 % CI], 0.013 [0.00-0.36]). The associations observed for FMI were similar.

CONCLUSIONS

In patients with RA, obesity, and a higher percentage of fatty tissue, intestinal microbiota differed from that of controls and of the other patients. The genus Dialister was associated with obesity and FMI.

Uncovering the Underworld of Axial Spondyloarthritis

Axial spondyloarthritis (axial-SpA) is a multifactorial disease characterized by inflammation in sacroiliac joints and spine, bone reabsorption, and aberrant bone deposition, which may lead to ankylosis. Disease pathogenesis depends on genetic, immunological, mechanical, and bioenvironmental factors. HLA-B27 represents the most important genetic factor, although the disease may also develop in its absence. This MHC class I molecule has been deeply studied from a molecular point of view. Different theories, including the arthritogenic peptide, the unfolded protein response, and HLA-B27 homodimers formation, have been proposed to explain its role. From an immunological point of view, a complex interplay between the innate and adaptive immune system is involved in disease onset. Unlike other systemic autoimmune diseases, the innate immune system in axial-SpA has a crucial role marked by abnormal activity of innate immune cells, including γδ T cells, type 3 innate lymphoid cells, neutrophils, and mucosal-associated invariant T cells, at tissue-specific sites prone to the disease. On the other hand, a T cell adaptive response would seem involved in axial-SpA pathogenesis as emphasized by several studies focusing on TCR low clonal heterogeneity and clonal expansions as well as an interindividual sharing of CD4/8 T cell receptors. As a result of this immune dysregulation, several proinflammatory molecules are produced following the activation of tangled intracellular pathways involved in pathomechanisms of axial-SpA. This review aims to expand the current understanding of axial-SpA pathogenesis, pointing out novel molecular mechanisms leading to disease development and to further investigate potential therapeutic targets.

Are Patients with Axial Spondyloarthritis Who Were Breastfed Protected against the Development of Severe Disease?

BACKGROUND AND AIMS

Breastfeeding is recognized as one of the most influential drivers of the gut microbiome. In turn, alterations in the gut microbiome may play a role in the development and severity of spondyloarthritis (SpA). We aimed to analyze different disease outcomes in patients with axial SpA (axSpA) based on the history of breastfeeding.

PATIENTS AND METHODS

A random sample was selected from a large database of axSpA patients. Patients were divided based on history of breastfeeding and several disease outcomes were compared. Both groups were also compared based on disease severity. Adjusted linear and logistic regression statistical methods were used.

RESULTS

The study included 105 patients (46 women and 59 men), and the median age was 45 years (IQR: 16-72), and the mean age at diagnosis was 34.3 ± 10.9 years. Sixty-one patients (58.1%) were breastfed, with a median duration of 4 (IQR: 1-24) months. After the fully adjusted model, BASDAI [-1.13 (95%CI: -2.04, -0.23), p = 0.015] and ASDAS [-0.38 (95%CI: -0.72, -0.04), p = 0.030] scores were significantly lower in breastfed patients. Forty-two percent had severe disease. In the adjusted logistic model for age, sex, disease duration, family history, HLA-B27, biologic therapy, smoking, and obesity, breastfeeding had a protective effect against the development of severe disease (OR 0.22, 95%CI: 0.08-0.57, p = 0.003). The selected sample size was sufficient to detect this difference with a statistical power of 87% and a confidence level of 95%.

CONCLUSION

Breastfeeding might exert a protective effect against severe disease in patients with axSpA. These data need further confirmation.

No Evidence of a Genetic Causal Relationship between Ankylosing Spondylitis and Gut Microbiota: A Two-Sample Mendelian Randomization Study

Objective: Ankylosing spondylitis (AS) is associated with a variety of gut microbiotas. We aim to analyze the causal relationship between the two at the genetic level. Methods: Mendelian randomization (MR) is a type of instrumental variables (IVs) analysis; MR follows the Mendelian genetic rule of "parental alleles are randomly assigned to offspring" and takes genetic variation as IVs to infer the causal association between exposure factors and study outcome in observational studies. Genome-wide association study (GWAS) summary data of AS were from the FinnGen consortium, and the gut microbiota (Bacteroides, Streptococcus, Proteobacteria, Lachnospiraceae) were from the MiBioGen consortium. The TwoSampleMR and MRPRESSO packages of the R were used to perform a two-sample MR study. Random-effects inverse variance weighted (IVW) was the main analysis method, and MR Egger, weighted median, simple mode, and weighted mode were used as supplementary methods. We examined heterogeneity and horizontal pleiotropy, and examined whether the analysis results were influenced by a single SNP. We applied radial variants of the IVW and MR-Egger model for the improved visualization of the causal estimate. We further examined the causal relationship between AS and gut microbiota, and the robustness of the analysis results. Finally, we performed maximum likelihood, penalized weighted median, and IVW (fixed effects) to further identify the potential causal association. Results: The random-effects IVW results showed that Bacteroides (p = 0.965, OR 95% confidence interval [CI] = 0.990 [0.621-1.579]), Streptococcus (p = 0.591, OR 95% CI = 1.120 [0.741-1.692]), Proteobacteria (p = 0.522, OR 95% CI = 1.160 [0.737-1.826]), and Lachnospiraceae (p = 0.717, OR 95% CI = 1.073 [0.732-1.574]) have no genetic causal relationship with AS. There was no heterogeneity, horizontal pleiotropy or outliers, and results were normally distributed. The MR analysis results were not driven by a single SNP. Conclusions: This study showed that Bacteroides, Streptococcus, Proteobacteria and Lachnospiraceae, four common gut microbiotas associated with AS, had no causal relationship with AS at the genetic level. This study makes a positive contribution to the genetics of AS, but the insufficient number of gut microbiota included is a limitation.

The microbiome in HLA-B27-associated disease: implications for acute anterior uveitis and recommendations for future studies

The pathogenesis of human leukocyte antigen (HLA)-B27-associated diseases such as acute anterior uveitis (AAU) and ankylosing spondylitis (AS) remains poorly understood, though Gram-negative bacteria and subclinical bowel inflammation are strongly implicated. Accumulating evidence from animal models and clinical studies supports several hypotheses, including HLA-B27-dependent dysbiosis, altered intestinal permeability, and molecular mimicry. However, the existing literature is hampered by inadequate studies designed to establish causation or uncover the role of viruses and fungi. Moreover, the unique disease model afforded by AAU to study the gut microbiota has been neglected. This review critically evaluates the current literature and prevailing hypotheses on the link between the gut microbiota and HLA-B27-associated disease. We propose a new potential role for HLA-B27-driven altered antibody responses to gut microbiota in disease pathogenesis and outline recommendations for future well-controlled human studies, focusing on AAU.

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.

Interactions between NSAIDs, opioids and the gut microbiota - Future perspectives in the management of inflammation and pain

The composition of intestinal microbiota is influenced by a number of factors, including medications, which may have a substantial impact on host physiology. Nonsteroidal anti-inflammatory drugs (NSAIDs) and opioid analgesics are among those widely used medications that have been shown to alter microbiota composition in both animals and humans. Although much effort has been devoted to identify microbiota signatures associated with these medications, much less is known about the underlying mechanisms. Mucosal inflammation, changes in intestinal motility, luminal pH and bile acid metabolism, or direct drug-induced inhibitory effect on bacterial growth are all potential contributors to NSAID- and opioid-induced dysbiosis, however, only a few studies have addressed directly these issues. In addition, there is a notable overlap between the microbiota signatures of these drugs and certain diseases in which they are used, such as spondyloarthritis (SpA), rheumatoid arthritis (RA) and neuropathic pain associated with type 2 diabetes (T2D). The aims of the present review are threefold. First, we aim to provide a comprehensive up-to-date summary on the bacterial alterations caused by NSAIDs and opioids. Second, we critically review the available data on the possible underlying mechanisms of dysbiosis. Third, we review the current knowledge on gut dysbiosis associated with SpA, RA and neuropathic pain in T2D, and highlight the similarities between them and those caused by NSAIDs and opioids. We posit that drug-induced dysbiosis may contribute to the persistence of these diseases, and may potentially limit the therapeutic effect of these medications by long-term use. In this context, we will review the available literature data on the effect of probiotic supplementation and fecal microbiota transplantation on the therapeutic efficacy of NSAIDs and opioids in these diseases.

Sex differences in musculoskeletal injury and disease risks across the lifespan: Are there unique subsets of females at higher risk than males for these conditions at distinct stages of the life cycle?

Sex differences have been reported for diseases of the musculoskeletal system (MSK) as well as the risk for injuries to tissues of the MSK system. For females, some of these occur prior to the onset of puberty, following the onset of puberty, and following the onset of menopause. Therefore, they can occur across the lifespan. While some conditions are related to immune dysfunction, others are associated with specific tissues of the MSK more directly. Based on this life spectrum of sex differences in both risk for injury and onset of diseases, a role for sex hormones in the initiation and progression of this risk is somewhat variable. Sex hormone receptor expression and functioning can also vary with life events such as the menstrual cycle in females, with different tissues being affected. Furthermore, some sex hormone receptors can affect gene expression independent of sex hormones and some transitional events such as puberty are accompanied by epigenetic alterations that can further lead to sex differences in MSK gene regulation. Some of the sex differences in injury risk and the post-menopausal disease risk may be "imprinted" in the genomes of females and males during development and sex hormones and their consequences only modulators of such risks later in life as the sex hormone milieu changes. The purpose of this review is to discuss some of the relevant conditions associated with sex differences in risks for loss of MSK tissue integrity across the lifespan, and further discuss several of the implications of their variable relationship with sex hormones, their receptors and life events.

Functional recovery outcomes following acute stroke is associated with abundance of gut microbiota related to inflammation, butyrate and secondary bile acid

Accumulating evidence suggests that gut microbes modulate brain plasticity via the bidirectional gut-brain axis and play a role in stroke rehabilitation. However, the microbial species alterations associated with stroke and their correlation with functional outcome measures following acute stroke remain unknown. Here we measure post-stroke gut dysbiosis and how it correlates with gut permeability and cognitive functions in 12 stroke participants, 18 controls with risk factors for stroke, and 12 controls without risk factors. Stool samples were used to measure the microbiome with whole genome shotgun sequencing and leaky gut markers. We genotyped APOE status and measured diet composition and motor, cognitive, and emotional status using NIH Toolbox. We used linear regression methods to identify gut microbial associations with cognitive and emotional assessments. We did not find significance differences between the two control groups. In contrast, the bacteria populations of the Stroke group were statistically dissimilar from the control groups. Relative abundance analysis revealed notable decreases in butyrate-producing microbial taxa, secondary bile acid-producing taxa, and equol-producing taxa. The Stroke group had higher levels of the leaky gut marker alpha-1-antitrypsin in the stool than either of the groups and several taxa including Roseburia species (a butyrate producer) were negatively correlated with alpha-1-antitrypsin. Stroke participants scored lower on memory testing than those in the two control groups. Stroke participants with more Roseburia performed better on the picture vocabulary task; more Bacteroides uniformis (a butyrate producer) and less Escherichia coli (a pro-inflammatory species) reported higher levels of self-efficacy. Intakes of fiber, fruit and vegetable were lower, but sweetened beverages were higher, in the Stroke group compared with controls. Vegetable consumption was correlated with many bacterial changes among the participants, but only the species Clostridium bolteae, a pro-inflammatory species, was significantly associated with stroke. Our findings indicate that stroke is associated with a higher abundance of proinflammatory species and a lower abundance of butyrate producers and secondary bile acid producers. These altered microbial communities are associated with poorer functional performances. Future studies targeting the gut microbiome should be developed to elucidate whether its manipulation could optimize rehabilitation and boost recovery.

Role of Intestinal Dysbiosis and Nutrition in Rheumatoid Arthritis

Rheumatoid arthritis is a chronic systemic immune-mediated disease caused by genetic and environmental factors. It is often characterized by the generation of autoantibodies that lead to synovial inflammation and eventual multi-joint destruction. A growing number of studies have shown significant differences in the gut microbiota composition of rheumatoid arthritis (RA) patients compared to healthy controls. Environmental factors, and changes in diet and nutrition are thought to play a role in developing this dysbiosis. This review aims to summarize the current knowledge of intestinal dysbiosis, the role of nutritional factors, and its implications in the pathogenesis of rheumatoid arthritis and autoimmunity. The future direction focuses on developing microbiome manipulation therapeutics for RA disease management.

A glance into the future of diagnosis and treatment of spondyloarthritis

The last two decades have seen major developments in the field of spondyloarthritis (SpA), but there are still important unmet needs to address. In the future, we envisage important advances in the diagnosis and treatment of SpA. In the diagnosis of SpA, the use of online and social media tools will increase awareness of the disease and facilitate the referral of patients to rheumatology clinics. In addition, more specific diagnostic tests will be available, especially advanced imaging methods and new biomarkers. This will allow most patients to be diagnosed at an early stage of the disease. In the treatment of SpA, an increasing number of novel treatment targets can be expected, most of which will be directed against intracellular enzymes. We hope to see more strategy trials shaping treatment pathways in SpA and accommodating principals of precision medicine. Approved treatment options will be available for both axial and peripheral SpA. We also hope to intervene not only at the inflammation level but also at the level of underlying immunological processes that might be associated with a higher probability of long-standing remission if not a cure. Finally, artificial intelligence techniques will allow for the analysis of large-scale data to answer relevant research questions for the diagnosis and management of patients with SpA.

Symptoms Compatible with Rome IV Functional Bowel Disorder in Patients with Ankylosing Spondylitis

OBJECTIVES

To determine the frequency of symptoms meeting Rome IV functional bowel disorder (FBD) in patients with ankylosing spondylitis (AS), investigate factors associated with FBD symptoms, and assess whether having FBD symptoms might influence AS disease activity.

METHODS

In this cross-sectional study, we enrolled 153 AS patients without known colonic ulcer and 56 sex- and age-matched controls to evaluate FBD (or its subtypes) symptoms. Disease characteristics were also evaluated in AS group.

RESULTS

Sixty (39.2%) of 153 AS patients had FBD symptoms, which was more prevalent than controls (23.2%). Besides, symptoms compatible with irritable bowel syndrome (IBS) and chronic diarrhea were detected in 18 and 43 AS patients respectively. For AS group, multivariable logistic regression analyses showed that symptoms of FBD, IBS, and chronic diarrhea were negatively associated with using non-steroidal anti-inflammatory drug (NSAID), and positively associated with comorbid fibromyalgia, respectively. In exploration about effects of FBD (or its subtypes) symptoms on AS disease activity by multivariable linear regression analyses, FBD symptoms and chronic diarrhea had universal positive associations with assessments of AS disease characteristics respectively.

CONCLUSION

Patients with AS had frequent symptoms compatible with FBD, IBS, and chronic diarrhea, proportions of which were lower in those with NSAID-use. The improvement of FBD symptoms and chronic diarrhea might be conducive to disease status of AS patients.

Gut dysbiosis in rheumatic diseases: A systematic review and meta-analysis of 92 observational studies

Background

Emerging evidence suggests that dysbiosis in gut microbiota may contribute to the occurrence or development of several rheumatic diseases. Since gut microbiota dysbiosis is potentially modifiable, it has been postulated to be a promising preventive or therapeutic target for rheumatic diseases. However, the current understanding on the potential associations between gut microbiota and rheumatic diseases is still inadequate. Therefore, we aimed to synthesise the accumulating evidence for the relation of gut microbiota to rheumatic diseases.

Methods

The PubMed, Embase and Cochrane Library were searched from inception to March 11, 2022 to include observational studies evaluating the associations between gut microbiota and rheumatic diseases. Standardised mean difference (SMD) of α-diversity indices between rheumatic diseases and controls were estimated using random-effects model. β-diversity indices and relative abundance of gut microbes were summarised qualitatively.

Findings

Of the included 92 studies (11,998 participants), 68 provided data for α-diversity. Taken together as a whole, decreases in α-diversity indices were consistently found in rheumatic diseases (observed species: SMD = −0.36, [95%CI = −0.63, −0.09]; Chao1: SMD = −0.57, [95%CI = −0.88, −0.26]; Shannon index: SMD = −0.33, [95%CI = −0.48, −0.17]; Simpson index: SMD = −0.32, [95%CI = −0.49, −0.14]). However, when specific rheumatic diseases were examined, decreases were only observed in rheumatoid arthritis (observed species: SMD = −0.51, [95%CI = −0.78, −0.24]; Shannon index: SMD = −0.31, [95%CI = −0.49, −0.13]; Simpson index: SMD = −0.31, [95%CI = −0.54, −0.08]), systemic lupus erythematosus (Chao1: SMD = −1.60, [95%CI = −2.54, −0.66]; Shannon index: SMD = −0.63, [95%CI = −1.08, −0.18]), gout (Simpson index: SMD = −0.64, [95%CI = −1.07, −0.22]) and fibromyalgia (Simpson index: SMD = −0.28, [95%CI = −0.44, −0.11]), whereas an increase was observed in systemic sclerosis (Shannon index: SMD = 1.25, [95%CI = 0.09, 2.41]). Differences with statistical significance in β-diversity were consistently reported in ankylosing spondylitis and IgG4-related diseases. Although little evidence of disease specificity of gut microbes was found, shared alterations of the depletion of anti-inflammatory butyrate-producing microbe (i.e., Faecalibacterium) and the enrichment of pro-inflammatory microbe (i.e., Streptococcus) were observed in rheumatoid arthritis, Sjögren's syndrome and systemic lupus erythematosus.

Interpretation

Gut microbiota dysbiosis was associated with rheumatic diseases, principally with potentially non-specific, shared alterations of microbes.

Funding

National Natural Science Foundation of China (81930071, 81902265, 82072502 and U21A20352).

Monocytes and Macrophages in Spondyloarthritis: Functional Roles and Effects of Current Therapies

Spondyloarthritis (SpA) is a family of chronic inflammatory diseases, being the most prevalent ankylosing spondylitis (AS) and psoriatic arthritis (PsA). These diseases share genetic, clinical and immunological features, such as the implication of human leukocyte antigen (HLA) class I molecule 27 (HLA-B27), the inflammation of peripheral, spine and sacroiliac joints and the presence of extra-articular manifestations (psoriasis, anterior uveitis, enthesitis and inflammatory bowel disease). Monocytes and macrophages are essential cells of the innate immune system and are the first line of defence against external agents. In rheumatic diseases including SpA, the frequency and phenotypic and functional characteristics of both cell types are deregulated and are involved in the pathogenesis of these diseases. In fact, monocytes and macrophages play key roles in the inflammatory processes characteristics of SpA. The aim of this review is analysing the characteristics and functional roles of monocytes and macrophages in these diseases, as well as the impact of different current therapies on these cell types.