How the microbiota shapes rheumatic diseases

The impacts of obesity in rheumatoid arthritis and insights into therapeutic purinergic modulation

Rheumatoid Arthritis (RA) is an autoimmune condition responsible for the impairment of synovia and joints, endangering the functionality of individuals and contributing to mortality. Currently, obesity is increasing worldwide, and recent studies have suggested an association between such condition and RA. In this sense, obese individuals present a lower capacity for achieving remission and present more intense symptoms of the disease, demonstrating a link between both disorders. Different studies aim to understand the possible connection between the conditions; however, few is known in this sense. Therefore, knowing that obesity can alter the activity of multiple body systems, this work's objective is to evaluate the main modifications caused by obesity, which can be linked to the pathophysiology of RA, highlighting as relevant topics obesity's negative impact triggering systemic inflammation, intestinal dysbiosis, endocrine disbalances. Furthermore, the relationship between oxidative stress and obesity also deserves to be highlighted, considering the influence of reactive oxygen species (ROS) accumulation in RA exacerbation. Additionally, many of those characteristics influenced by obesity, along with the classic peculiarities of RA pathophysiology, can also be associated with purinergic signaling. Hence, this work suggests possible connections between the purinergic system and RA, proposing potential therapeutic targets against RA to be studied.

Neutrophil IL-26 fuels autoinflammation

Pustular psoriasis is an inflammatory skin disease with features of neutrophil-mediated sterile autoinflammation. In this issue of JEM, Baldo et al. (https://doi.org/10.1084/jem.20231464) show that this autoinflammation is driven by a vicious cycle through neutrophil-derived IL-26.

Axial Spondyloarthritis: an overview of the disease

Axial Spondyloarthritis (axSpA) is a chronic, inflammatory, immune-mediated rheumatic disease that comprises two subsets, non-radiographic and radiographic axSpA, and belongs to a heterogeneous group of spondyloarthritides (SpA). Over the years, the concept of SpA has evolved significantly, as reflected in the existing classification criteria. Considerable progress has been made in understanding the genetic and immunological basis of axSpA, in studying the processes of chronic inflammation and pathological new bone formation, which are pathognomonic for the disease. As a result, new medication therapies were developed, which bring more effective ways for disease control. This review presents a brief overview of the literature related to these aspects of disease after summarising the available information on the topic that we considered relevant. Specifically, it delves into recent research illuminating the primary pathological processes of enthesitis and associated osteitis in the context of inflammation in axSpA. The exploration extends to discussion of inflammatory pathways, with a particular focus on Th1/Th17-mediated immunity and molecular signaling pathways of syndesmophyte formation. Additionally, the review sheds light on the pivotal role of cytokine dysregulation, highlighting the significance of the IL-23/17 axis and TNF-α in this intricate network of immune responses which is decisive for therapeutic approaches in the disease.

Role of Synbiotics (Prebiotics and Probiotics) as Dietary Supplements in Type 2 Diabetes Mellitus Induced Health Complications

Diabetes is a metabolic disorder whose prevalence has become a worrying condition in recent decades. Chronic diabetes can result in serious health conditions such as impaired kidney function, stroke, blindness, and myocardial infarction. Despite a variety of currently available treatments, cases of diabetes and its complications are on the rise. This review article provides a comprehensive account of the ameliorative effect of prebiotics and probiotics individually or in combination i.e. synbiotics on health complications induced by Type 2 Diabetes Mellitus (T2DM). Recent advances in the field underscore encouraging outcomes suggesting the consumption of synbiotics leads to favorable changes in the gut microbiota. These changes result in the production of bioactive metabolites such as short-chain fatty acids (crucial for lowering blood sugar levels), reducing inflammation, preventing insulin resistance, and encouraging the release of glucagon-like peptide-1 in the host. Notably, novel strategies supplementing synbiotics to support gut microbiota are gaining attraction as pivotal interventions in mitigating T2DM-induced health complications. Thus, by nurturing a symbiotic relationship between prebiotics and probiotics i.e. synbiotics, these interventions hold promise in reshaping the microbial landscape of the gut thereby offering a multifaceted approach to managing T2DM and its associated morbidities. Supporting the potential of synbiotics underscores a paradigm shift toward holistic and targeted interventions in diabetes management, offering prospects for improved outcomes and enhanced quality of life for affected individuals. Nevertheless, more research needs to be done to better understand the single and multispecies pre/pro and synbiotics in the prevention and management of T2DM-induced health complications.

Association between primary Sjögren's syndrome and gut microbiota disruption: a systematic review and meta-analysis

Evidence of gut microbiota disruption for numerous autoimmune diseases has accumulated. Recently, the relationship between the microbiota and primary Sjögren's disease has been increasingly investigated but has yet to be systematically elucidated. Therefore, a meta-analysis of publications dealing on topic was conducted. Case-control studies comparing primary Sjögren's syndrome patients and healthy controls (HCs) were systematically searched in nine databases from inception to March 1, 2023. The primary result quantitatively evaluated in this meta-analysis was the α-diversity. The secondary results qualitatively extracted and analyzed were the β-diversity and relative abundance. In total, 22 case-control studies covering 915 pSS patients and 2103 HCs were examined. The quantitative analysis revealed a slight reduction in α-diversity in pSS patients compared to HCs, with a lower Shannon-Wiener index (SMD =  - 0.46, (- 0.68, - 0.25), p < 0.0001, I2 = 71%), Chao1 richness estimator (SMD =  - 0.59, (- 0.86, - 0.32), p < 0.0001, I2 = 81%), and ACE index (SMD =  - 0.92, (- 1.64, - 0.19), p = 0.01, I2 = 86%). However, the Simpson index (SMD = 0.01, (- 0.43, 0.46) p = 0.95, I2 = 86%) was similar in the two groups. The β-diversity significantly differed between pSS patients and HCs. Variations in the abundance of specific microbes and their metabolites and potential functions contribute to the pSS pathogenesis. Notably, the abundance of the phylum Firmicutes decreased, while that of Proteobacteria increased. SCFA-producing microbes including Ruminococcaceae, Lachnospiraceae, Faecalibacterium, Butyricicoccus, and Eubacterium hallii were depleted. In addition to diversity, the abundances of some specific microbes were related to clinical parameters. According to this systematic review and meta-analysis, gut microbiota dysbiosis, including reduced diversity, was associated with proinflammatory bacterium enrichment and anti-inflammatory bacterium depletion in pSS patients. Further research on the relationship between the gut microbiota and pSS is warranted.

Gut microbial community and fecal metabolomic signatures in different types of osteoporosis animal models

BACKGROUND

The gut microbiota (GM) constitutes a critical factor in the maintenance of physiological homeostasis. Numerous studies have empirically demonstrated that the GM is closely associated with the onset and progression of osteoporosis (OP). Nevertheless, the characteristics of the GM and its metabolites related to different forms of OP are poorly understood. In the present study, we examined the changes in the GM and its metabolites associated with various types of OP as well as the correlations among them.

METHODS

We simultaneously established rat postmenopausal, disuse-induced, and glucocorticoid-induced OP models. We used micro-CT and histological analyses to observe bone microstructure, three-point bending tests to measure bone strength, and enzyme-linked immunosorbent assay (ELISA) to evaluate the biochemical markers of bone turnover in the three rat OP models and the control. We applied 16s rDNA to analyze GM abundance and employed untargeted metabolomics to identify fecal metabolites in all four treatment groups. We implemented multi-omics methods to explore the relationships among OP, the GM, and its metabolites.

RESULTS

The 16S rDNA sequencing revealed that both the abundance and alterations of the GM significantly differed among the OP groups. In the postmenopausal OP model, the bacterial genera g__Bacteroidetes_unclassified, g__Firmicutes_unclassified, and g__Eggerthella had changed. In the disuse-induced and glucocorticoid-induced OP models, g__Akkermansia and g__Rothia changed, respectively. Untargeted metabolomics disclosed that the GM-derived metabolites significantly differed among the OP types. However, a Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that it was mainly metabolites implicated in lipid and amino acid metabolism that were altered in all cases. An association analysis indicated that the histidine metabolism intermediate 4-(β-acetylaminoethyl) imidazole was common to all OP forms and was strongly correlated with all bone metabolism-related bacterial genera. Hence, 4-(β-acetylaminoethyl) imidazole might play a vital role in OP onset and progression.

CONCLUSIONS

The present work revealed the alterations in the GM and its metabolites that are associated with OP. It also disclosed the changes in the GM that are characteristic of each type of OP. Future research should endeavor to determine the causal and regulatory effects of the GM and the metabolites typical of each form of OP.

The gut ecosystem and immune tolerance

The gastrointestinal tract is home to the largest microbial population in the human body. The gut microbiota plays significant roles in the development of the gut immune system and has a substantial impact on the maintenance of immune tolerance beginning in early life. These microbes interact with the immune system in a dynamic and interdependent manner. They generate immune signals by presenting a vast repertoire of antigenic determinants and microbial metabolites that influence the development, maturation and maintenance of immunological function and homeostasis. At the same time, both the innate and adaptive immune systems are involved in modulating a stable microbial ecosystem between the commensal and pathogenic microorganisms. Hence, the gut microbial population and the host immune system work together to maintain immune homeostasis synergistically. In susceptible hosts, disruption of such a harmonious state can greatly affect human health and lead to various auto-inflammatory and autoimmune disorders. In this review, we discuss our current understanding of the interactions between the gut microbiota and immunity with an emphasis on: a) important players of gut innate and adaptive immunity; b) the contribution of gut microbial metabolites; and c) the effect of disruption of innate and adaptive immunity as well as alteration of gut microbiome on the molecular mechanisms driving autoimmunity in various autoimmune diseases.

Progress of linking gut microbiota and musculoskeletal health: casualty, mechanisms, and translational values

The musculoskeletal system is important for balancing metabolic activity and maintaining health. Recent studies have shown that distortions in homeostasis of the intestinal microbiota are correlated with or may even contribute to abnormalities in musculoskeletal system function. Research has also shown that the intestinal flora and its secondary metabolites can impact the musculoskeletal system by regulating various phenomena, such as inflammation and immune and metabolic activities. Most of the existing literature supports that reasonable nutritional intervention helps to improve and maintain the homeostasis of intestinal microbiota, and may have a positive impact on musculoskeletal health. The purpose of organizing, summarizing and discussing the existing literature is to explore whether the intervention methods, including nutritional supplement and moderate exercise, can affect the muscle and bone health by regulating the microecology of the intestinal flora. More in-depth efficacy verification experiments will be helpful for clinical applications.

Probiotics and Their Role in the Management of Type 2 Diabetes Mellitus (Short-Term Versus Long-Term Effect): A Systematic Review and Meta-Analysis

Diabetes is a major economic burden and an illness with a rising incidence worldwide. Type 2 diabetes mellitus (T2DM), the most prevalent kind of diabetes, is characterized by insulin resistance and insufficient insulin production. Recent research has implicated gut microbiota dysbiosis as a contributing factor to T2DM pathogenesis. The present study employed a methodology based on randomized controlled trials (RCTs) to assess the therapeutic efficacy of probiotics in the treatment of T2DM. A thorough search was done in PubMed and Medline for articles written in English and published between 2017 and 2023. Studies were chosen based on predetermined inclusion criteria, and the search technique adhered to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) principles. This study also employed a robust assessment instrument, widely recognized in the medical and health sciences, to evaluate the potential presence of bias within the selected research studies. Out of 96 identified articles, 22 RCTs met the eligibility criteria. Both short-term (8 weeks or less) and long-term (12 weeks or more) probiotic administrations were made. The results of the meta-analysis demonstrated a significant improvement in the homeostatic model assessment of insulin resistance (HOMA-IR) following the probiotic intervention (P=0.02) and considerably decreased glycated hemoglobin HbA1c levels (P=0.004) and fasting blood glucose (FBG) levels (P<0.0001) in T2DM patients compared to placebo. This research offers proof that probiotics are clinically effective in the treatment of T2DM. Probiotic supplementation demonstrated favorable effects on glycemic control markers. However, the findings from RCTs were heterogeneous, and some studies showed inconsistent results. To clarify the processes underlying the probiotics' therapeutic benefits and to determine the best probiotic strains, doses, and therapy durations, more research is required. Nevertheless, probiotics offer a promising therapeutic approach for T2DM management and warrant consideration as a potential adjunct therapy in clinical practice.

Tripterygium hypoglaucum extract ameliorates adjuvant-induced arthritis in mice through the gut microbiota

Traditionally, Tripterygium hypoglaucum (Levl.) Hutch (THH) are widely used in Chinese folk to treat rheumatoid arthritis (RA). This study aimed to investigate whether the anti-RA effect of THH is related with the gut microbiota. The main components of prepared THH extract were identified by HPLC-MS. C57BL/6 mice with adjuvant-induced arthritis (AIA) were treated with THH extract by gavage for one month. THH extract significantly alleviated swollen ankle, joint cavity exudation, and articular cartilage destruction in AIA mice. The mRNA and protein levels of inflammatory mediators in muscles and plasma indicated that THH extract attenuated inflammatory responses in the joint by blocking TLR4/MyD88/MAPK signaling pathways. THH extract remarkably restored the dysbiosis of the gut microbiota in AIA mice, featuring the increases of Bifidobacterium, Akkermansia, and Lactobacillus and the decreases of Butyricimonas, Parabacteroides, and Anaeroplasma. Furthermore, the altered bacteria were closely correlated with physiological indices and drove metabolic changes of the intestinal microbiota. In addition, antibiotic-induced pseudo germ-free mice were employed to verify the role of the intestinal flora. Strikingly, THH treatment failed to ameliorate the arthritis symptoms and signaling pathways in pseudo germ-free mice, which validates the indispensable role of the intestinal flora. For the first time, we demonstrated that THH extract protects joint inflammation by manipulating the intestinal flora and regulating the TLR4/MyD88/MAPK signaling pathway. Therefore, THH extract may serve as a microbial modulator to recover RA in clincial practice.ver RA in clincial practice.

The Possible Role of Probiotic Supplementation in Inflammation: A Narrative Review

The fine balance between symbiotic and potentially opportunistic and/or pathogenic microorganisms can undergo quantitative alterations, which, when associated with low intestinal biodiversity, could be responsible for the development of gut inflammation and the so-called "intestinal dysbiosis". This condition is characterized by the disbalance of a fine synergistic mechanism involving the mucosal barrier, the intestinal neuroendocrine system, and the immune system that results in an acute inflammatory response induced by different causes, including viral or bacterial infections of the digestive tract. More frequently, however, dysbiosis is induced slowly and subtly by subliminal causal factors, resulting in a chronic condition related to different diseases affecting the digestive tract and other organs and apparatuses. Studies on animal models, together with studies on humans, highlight the significant role of the gut microbiota and microbiome in the occurrence of inflammatory conditions such as metabolic syndrome and cardiovascular diseases (CVDs); neurodegenerative, urologic, skin, liver, and kidney pathologies; and premature aging. The blood translocation of bacterial fragments has been found to be one of the processes linked to gut dysbiosis and responsible for the possible occurrence of "metabolic endotoxemia" and systemic inflammation, associated with an increased risk of oxidative stress and related diseases. In this context, supplementation with different probiotic strains has been shown to restore gut eubiosis, especially if administered in long-term treatments. The aim of this review is to describe the anti-inflammatory effects of specific probiotic strains observed in clinical trials and the respective indications, highlighting the differences in efficacy depending on strain, formulation, time and duration of treatment, and dosage used.

Lupus Nephritis and Dysbiosis

Lupus nephritis (LN) is one of the most common and serious complications of systemic lupus erythematosus (SLE). The risk factors for developing LN by SLE patients are not fully understood. They are considered to be a mix of genetic and environmental variables, one of them being dysbiosis, proposed recently to interfere with autoimmunity. As of yet, the relations between the human microbiome, its genetic determinants, individual variability and clinical consequences remain to be established. One of the major obstacles in studying them is the magnitude of confounders, such as diet, drugs, infections or antibiotics use. They also make comparison between the studies extremely complicated. We reviewed the available evidence for the interplay between microbiome, dysbiosis and mechanisms triggering the autoimmune responses and potentially contributing to LN development. One such mechanism is the stimulation of autoimmune responses by bacterial metabolites that can mimic autoantigens and cause antibody production. These mimicking microbial antigens seem to be a promising target for future interventions.

Gut dysbiosis in autoimmune diseases: Association with mortality

To better understand the impact of gut dysbiosis on four autoimmune diseases [Sjögren’s syndrome (SS), systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and multiple sclerosis (MS)], this review investigated the altered gut bacteria in each disease and the shared ones among the four diseases. The enriched gut bacteria shared by three of the four autoimmune diseases were Streptococcus, Prevotella, and Eggerthella, which are associated with autoantibody production or activation of Th17 cells in immune-related diseases. On the other hand, Faecalibacterium comprises depleted gut bacteria shared by patients with SLE, MS, and SS, which is associated with various anti-inflammatory activities. The indexes of gut dysbiosis, defined as the number of altered gut bacterial taxa divided by the number of studies in SLE, MS, RA, and SS, were 1.7, 1.8, 0.7, and 1.3, respectively. Interestingly, these values presented a positive correlation trend with the standardized mortality rates —2.66, 2.89, 1.54, and 1.41, respectively. In addition, shared altered gut bacteria among the autoimmune diseases may correlate with the prevalence of polyautoimmunity in patients with SLE, SS, RA, and MS, that is, 41 percent, 32.6 percent, 14 percent, and 1–16.6 percent, respectively. Overall, this review suggests that gut dysbiosis in autoimmune diseases may be closely related to the failure of the gut immune system to maintain homeostasis.

The star target in SLE: IL-17

PURPOSE

The purpose of this review is to discuss the significance of IL-17 in SLE and the potential of IL-17-targeted therapy.

BACKGROUND

Systemic lupus erythematosus (SLE) is an autoimmune disease that can affect many organs and tissues throughout the body. It is characterized by overactive B and T cells and loss of immune tolerance to autoantigens. Interleukin-17 (IL-17) is a cytokine that promotes inflammation and has been implicated in the pathogenesis of several autoimmune diseases as well as inflammatory diseases. In in vitro cellular experiments in lupus susceptible mice or SLE patients, there is substantial evidence that IL-17 is a highly promising therapeutic target.

METHODS

We searched papers from PubMed database using the search terms, such as interleukin-17, systemic lupus erythematosus, treatment targets, T cells, lupus nephritis, and other relevant terms.

RESULTS

We discuss in this paper the molecular mechanisms of IL-17 expression, Th17 cell proliferation, and the relationship between IL-17 and Th17. The significance of IL-17 in SLE and the potential of IL-17-targeted therapy are further discussed in detail.

CONCLUSION

IL-17 has a very high potential for the development as a star target in SLE.

Gut-joint axis: Gut dysbiosis can contribute to the onset of rheumatoid arthritis via multiple pathways

Rheumatoid Arthritis (RA) is an autoimmune disease characterized by loss of immune tolerance and chronic inflammation. It is pathogenesis complex and includes interaction between genetic and environmental factors. Current evidence supports the hypothesis that gut dysbiosis may play the role of environmental triggers of arthritis in animals and humans. Progress in the understanding of the gut microbiome and RA. has been remarkable in the last decade. In vitro and in vivo experiments revealed that gut dysbiosis could shape the immune system and cause persistent immune inflammatory responses. Furthermore, gut dysbiosis could induce alterations in intestinal permeability, which have been found to predate arthritis onset. In contrast, metabolites derived from the intestinal microbiota have an immunomodulatory and anti-inflammatory effect. However, the precise underlying mechanisms by which gut dysbiosis induces the development of arthritis remain elusive. This review aimed to highlight the mechanisms by which gut dysbiosis could contribute to the pathogenesis of RA. The overall data showed that gut dysbiosis could contribute to RA pathogenesis by multiple pathways, including alterations in gut barrier function, molecular mimicry, gut dysbiosis influences the activation and the differentiation of innate and acquired immune cells, cross-talk between gut microbiota-derived metabolites and immune cells, and alterations in the microenvironment. The relative weight of each of these mechanisms in RA pathogenesis remains uncertain. Recent studies showed a substantial role for gut microbiota-derived metabolites pathway, especially butyrate, in the RA pathogenesis.

Effects of intestinal microbes on rheumatic diseases: A bibliometric analysis

Background

Rheumatic diseases (RD) are a group of multi-system inflammatory autoimmune diseases whose causes are still under study. In the past few decades, researchers have found traces of the association between rheumatic diseases and intestinal microbiota, which can partially explain the pathogenesis of rheumatic diseases. We aimed to describe the research trend and main divisions on how gut flora interreacts with rheumatic diseases, and discussed about the possible clinical applications.

Methods

We analyzed bibliometric data from the Web of Science core collection (dated 15th May 2022). Biblioshiny R language software packages (bibliometrix) were used to obtain the annual publication and citations, core sources according to Bradford's law, and country collaboration map. We designed and verified the keyword co-occurrence network and strategic diagram with the help of VOSviewer and CiteSpace, subdivided the research topic into several themes and identified research dimensions. The tables of most local cited documents and core sources were processed manually. Furthermore, the Altmetric Attention Score and the annual Altmetric Top 100 were applied to analyze the annual publication and citation.

Results

From a total of 541 documents, we found that the overall trend of annual publication and citation is increasing. The major research method is to compare the intestinal microbial composition of patients with certain rheumatic disease and that of the control group to determine microbial alterations related to the disease's occurrence and development. According to Bradford's law, the core sources are Arthritis and Rheumatology, Annals of the Rheumatic Diseases, Current Opinion in Rheumatology, Nutrients, Rheumatology, and Journal of Rheumatology. Since 1976, 101 countries or regions have participated in studies of rheumatology and intestinal microbes. The United States ranks at the top and has the broadest academic association with other countries. Five themes were identified, including the pivotal role of inflammation caused by intestinal bacteria in the rheumatic pathogenesis, the close relationship between rheumatic diseases and inflammatory bowel disease, immunoregulation mechanism as a mediator of the interaction between rheumatic diseases and gut flora, dysbiosis and decreased diversity in intestine of patients with rheumatic diseases, and the influence of oral flora on rheumatic diseases. Additionally, four research dimensions were identified, including pathology, treatment, disease, and experiments.

Conclusion

Studies on rheumatic diseases and the intestinal microbiota are growing. Attention should be paid to the mechanism of their interaction, such as the microbe-immune-RD crosstalk. Hopefully, the research achievements can be applied to diseases' prevention, diagnosis, and treatment, and our work can contribute to the readers' future research.

Succinate metabolism and its regulation of host-microbe interactions

Succinate is a circulating metabolite, and the relationship between abnormal changes in the physiological concentration of succinate and inflammatory diseases caused by the overreaction of certain immune cells has become a research focus. Recent investigations have shown that succinate produced by the gut microbiota has the potential to regulate host homeostasis and treat diseases such as inflammation. Gut microbes are important for maintaining intestinal homeostasis. Microbial metabolites serve as nutrients in energy metabolism, and act as signal molecules that stimulate host cell and organ function and affect the structural balance between symbiotic gut microorganisms. This review focuses on succinate as a metabolite of both host cells and gut microbes and its involvement in regulating the gut - immune tissue axis by activating intestinal mucosal cells, including macrophages, dendritic cells, and intestinal epithelial cells. We also examined its role as the mediator of microbiota - host crosstalk and its potential function in regulating intestinal microbiota homeostasis. This review explores feasible ways to moderate succinate levels and provides new insights into succinate as a potential target for microbial therapeutics for humans.

Enhanced Anti-Inflammatory Effect of the Combination of Lactiplantibacillus plantarum LS/07 with Methotrexate Compared to Their Monotherapies Studied in Experimental Arthritis

The gut microbiome (GM) of rheumatic arthritis (RA) patients is often altered in composition and function. Moreover, methotrexate (MTX), one of the most frequently used disease-modifying antirheumatic drugs, is known to negatively affect GM composition. The modulation of immune system activity is one of the therapeutic benefits of probiotics. The aim of the current investigation was to determine the impact of MTX therapy combined with one of the Lactobacillus strains, Lactoplantibacillus plantarum LS/07 (LB), on adjuvant arthritis (AA) in rats. Methods focused on biometric and inflammatory parameters in AA, particularly on plasmatic levels of IL-17A, MMP-9, and MCP-1, and the activities of gamma-glutamyl transferase in the spleen and joints were applied. Enhancing the effect of MTX, LB positively influenced all biometric and inflammatory parameters. The findings of the present study may be of help in proposing novel therapeutic strategies for RA patients.

Disease mechanisms in preclinical rheumatoid arthritis: A narrative review

In the last decades, the concept of preclinical rheumatoid arthritis (RA) has become established. In fact, the discovery that disease mechanisms start years before the onset of clinical RA has been one of the major recent insights in the understanding of RA pathogenesis. In accordance with the complex nature of the disease, preclinical events extend over several sequential phases. In a genetically predisposed host, environmental factors will further increase susceptibility for incident RA. In the initial steps of preclinical disease, immune disturbance mechanisms take place outside the joint compartment, namely in mucosal surfaces, such as the lung, gums or gut. Herein, the persistent immunologic response to altered antigens will lead to breach of tolerance and trigger autoimmunity. In a second phase, the immune response matures and is amplified at a systemic level, with epitope spreading and widening of the autoantibody repertoire. Finally, the synovial and bone compartment are targeted by specific autoantibodies against modified antigens, initiating a local inflammatory response that will eventually culminate in clinically evident synovitis. In this review, we discuss the elaborate disease mechanisms in place during preclinical RA, providing a broad perspective in the light of current evidence.

Separating the effects of childhood and adult body size on inflammatory arthritis: a Mendelian randomisation study

OBJECTIVES

Using Mendelian randomisation (MR), we examined whether childhood body size affects risk of rheumatoid arthritis (RA), ankylosing spondylitis (AS), psoriatic arthritis (PsA), gout and systemic lupus erythematosus (SLE) after accounting for the effect of adult body size.

METHODS

Genetic instruments for childhood (age 10 years) and adult body size were derived using data from 453 169 individuals from the UK Biobank study (313 and 580 variants respectively), which have been previously validated using body mass index data from three independent populations. Genome-wide association data comprised 22 350 RA, 9069 AS, 3609 PsA, 13 179 gout and 5201 SLE cases. For each outcome, we conducted univariable MR to estimate the total effects of childhood and adult body size, and multivariable MR to examine the independent effect of childhood body size after accounting for adult body size.

RESULTS

Genetically predicted childhood body size had a total effect on risk of PsA (OR 2.18 per change in body size category; 95% CI 1.43 to 3.31), gout (OR 2.18; 95% CI 1.43 to 3.31) and SLE (OR 2.44; 95% CI 1.14 to 5.22), but not RA (OR 0.95; 95% CI 0.70 to 1.29) or AS (OR 0.96; 95% CI 0.61 to 1.52). After accounting for adult body size, the direct effect of childhood body size was little changed for PsA (OR 1.92; 1.14 to 3.25) and SLE (OR 2.69; 1.24 to 5.87) but was attenuated for gout (OR 1.40; 95% CI 0.94 to 2.09).

CONCLUSIONS

Our findings suggest that, for PsA and SLE, the risk conferred from having a larger body size during childhood may not be fully reversable even when a healthy size is achieved in adulthood.

Lycium barbarum polysaccharide modulates gut microbiota to alleviate rheumatoid arthritis in a rat model

Rheumatoid arthritis (RA) seriously impairs the quality of life of sufferers. It has been shown that Lycium barbarum polysaccharide (LBP), a natural active indigestible ingredient with medicinal and edible functions, can effectively relieve RA, however, whether this effect is related to gut microbiota is not known. This study aimed to explore the RA alleviating mechanism of LBP mediated by gut microbiota using a collagen-induced arthritis rat model. The results showed that LBP significantly changed the gut microflora structure accompanied with the RA alleviation. Specifically, a LBP intervention reduced the relative abundance of Lachnospiraceae_NK4A136_group and uncultured_bacterium_f_Ruminococcaceae and significantly increased the abundance of Romboutsia, Lactobacillus, Dubosiella and Faecalibaculum. The mRNA contents of several colonic epithelial genes including Dpep3, Gstm6, Slc27a2, Col11a2, Sycp2, SNORA22, Tnni1, Gpnmb, Mypn and Acsl6, which are potentially associated to RA, were down-regulated due to the DNA hypermethylation, possibly caused by the elevating content of a bacterial metabolite S-adenosyl methionine (SAM). In conclusion, our current study suggests that LBP alleviated RA by reshaping the composition of intestinal microflora which may generate SAM, inducing DNA hypermethylation of RA-related genes in the host intestinal epithelium and subsequently reducing their expression.

In vitro triple coculture with gut microbiota from spondyloarthritis patients is characterized by inter-individual differences in inflammatory responses

Spondyloarthritis is a group of chronic inflammatory diseases that primarily affects axial or peripheral joints and is frequently associated with inflammation at non-articular sites. The disease is multifactorial, involving genetics, immunity and environmental factors, including the gut microbiota. In vivo, microbiome contributions are difficult to assess due to the multifactorial disease complexity. In a proof-of-concept approach, we therefore used a triple coculture model of immune-like, goblet and epithelial cells to investigate whether we could detect a differential impact from spondyloarthritis- vs. healthy-derived gut microbiota on host cell response. Despite their phylogenetic resemblance, flow cytometry-based phenotypic clustering revealed human-derived gut microbiota from healthy origin to cluster together and apart from spondyloarthritis donors. At host level, mucus production was higher upon exposure to healthy microbiota. Pro-inflammatory cytokine responses displayed more inter-individual variability in spondyloarthritis than in healthy donors. Interestingly, the high dominance in the initial sample of one patient of Prevotella, a genus previously linked to spondyloarthritis, resulted in the most differential host response upon 16 h host-microbe coincubation. While future research should further focus on inter-individual variability by using gut microbiota from a large cohort of patients, this study underscores the importance of the gut microbiota during the SpA disease course.

Microbiome Changes in Connective Tissue Diseases and Vasculitis: Focus on Metabolism and Inflammation

The microbial community acts as an active player in maintaining homeostasis and immune functions through a continuous and changeable cross-talk with the host immune system. Emerging evidence suggests that altered microbial composition, known as dysbiosis, might perturb the delicate balance between the microbiota and the immune system, triggering inflammation and potentially contributing to the pathogenesis and development of chronic inflammatory diseases. This review will summarize the current evidence about the microbiome-immunity cross-talk, especially focusing on the microbiota alterations described in patients with rheumatic diseases and on the recent findings concerning the interaction between microbiota, metabolic function, and the immune system.

Gut microbiome and daytime function in Chinese patients with major depressive disorder

BACKGROUND

Major depressive disorder (MDD) is underscored by daytime dysfunction-associated features, including mood disturbances, impaired cognition, fatigue, and daytime sleepiness. Importantly, the gut-brain axis may represent a potential mechanistic link between MDD and daytime dysfunction. Therefore, this study aimed to explore the gut microbiome composition and daytime dysfunction in Chinese patients with MDD.

METHODS

We enrolled 36 patients with MDD and 45 healthy controls (HCs) matched by age, sex, and body mass index (BMI). Daytime function including emotion, fatigue, and sleepiness were assessed using the Epworth Sleepiness Scale (ESS), Fatigue Severity Scale (FSS), Hamilton Anxiety Scale (HAMA), and Hamilton Depression Scale (HAMD). 16S rRNA sequencing was employed to characterize the gut microbiota in stool samples.

RESULTS

The operational taxonomic units (OTUs) OTU255, OUT363 were positively correlated with HAMD and HAMA. OTU244, OTU542 and OTU221 were positively correlated with ESS, HAMD and HAMA. OTU725 and OTU80 were positively correlated with FSS, ESS, HAMD and HAMA, while OTU423 and OTU502 were negatively correlated with all above. Flavonifractor positively correlated with fatigue in patients with MDD and all individuals simultaneously. The correlation between gut microbiome and daytime function was different in MDD and HCs.

CONCLUSIONS

We identified several OTUs associated with the severity of fatigue, depression, daytime sleepiness and anxiety in all individuals. Our results revealed the differences in microbiome found between patients with MDD and HCs. These findings provide insights into the potential microbiota changes that occur in MDD, and will enable the development of specific therapeutic strategies for targeting the various symptoms of depression.

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).

Gut microbial dysbiosis in rheumatoid arthritis: a systematic review protocol of case-control studies

INTRODUCTION

Rheumatoid arthritis (RA) has a huge societal impact due to the high prevalence, irreversible joint damage and systemic complications. Gut microbiota plays an important role in the pathogenesis and progression of RA by regulating the host immune system. Restoring intestinal homeostasis by altering the microbiota could be an attractive strategy for the prevention and treatment of RA. However, the signature features of microbial dysbiosis in RA are still controversial. Therefore, we aim to elucidate the characteristic change in the diversity and composition of gut microbiota in RA.

METHODS AND ANALYSIS

We will systematically search through PubMed, EMBASE, Web of Science and Cochrane Library, as well as dissertations and conference proceedings. The reference lists of all included studies will be also reviewed to retrieve additional relevant studies. The case-control studies that reported either the relative abundance of bacteria at the phylum or genus level or at least one of the alpha-diversity, beta-diversity indexes in both RA and healthy controls will be included. Eligible studies will be screened independently by two reviewers according to the inclusion criteria. The Newcastle-Ottawa Quality Assessment Scale will be used to assess the quality of the included studies. Data extraction, qualitative and quantitative analysis will be performed within the gut microbial dysbiosis in RA. The expected outcomes will be the identification of the specific changes in composition and diversity of the gut microbiota in patients with RA. The quality of evidence will be assessed by the Grading of Recommendations Assessment, Development and Evaluation framework.

ETHICS AND DISSEMINATION

Ethical approval is unnecessary as this review does not address the data and privacy of patients. The results will be published in a peer-reviewed scientific journal and conference presentations.

PROSPERO REGISTRATION NUMBER

CRD42021225229.

The Interplay Between Gut Microbiota and miRNAs in Cardiovascular Diseases

The human microbiota contains microorganisms found on the skin, mucosal surfaces and in other tissues. The major component, the gut microbiota, can be influenced by diet, genetics, and environmental factors. Any change in its composition results in pathophysiological changes that can further influence the evolution of different conditions, including cardiovascular diseases (CVDs). The microbiome is a complex ecosystem and can be considered the metagenome of the microbiota. MicroRNAs (miRNAs) are speculated to interact with the intestinal microbiota for modulating gene expressions of the host. miRNAs represent a category of small non-coding RNAs, consisting of approximately 22 nucleotides, which can regulate gene expression at post-transcriptional level, by influencing the degradation of mRNA and modifying protein amounts. miRNAs display a multitude of roles, being able to influence the pathogenesis and progression of various diseases. Circulating miRNAs are stable against degradation, due to their enclosure into extracellular vesicles (EVs). This review aims to assess the current knowledge of the possible interactions between gut microbiota, miRNAs, and CVDs. As more scientific research is conducted, it can be speculated that personalized patient care in the future may include the management of gut microbiota composition and the targeted treatment against certain expression of miRNAs.

The effect of probiotic cheese consumption on inflammatory and anti-inflammatory markers, disease severity, and symptoms in patients with rheumatoid arthritis: study protocol for a randomized, double-blind, placebo-controlled trial

Background

In recent decades, several studies have shown changes in the intestinal microflora among patients with rheumatoid arthritis (RA). Therapeutic measures using probiotics have shown favorable effects on the recovery of these patients. However, most studies have used probiotic supplements. In this study, we aimed to investigate the effect of probiotic cheese consumption on inflammatory and anti-inflammatory factors, disease severity, and symptoms in these patients.

Methods

This study is a randomized, double-blind clinical trial, in which forty patients with mild to moderate severity of RA will be randomly allocated to receive either 30 g/day probiotic cheese (n = 20) or only low-salt and low-fat cheese without any added probiotic (n = 20) for 12 weeks. Assessment of anthropometric measures and biochemical indicators, including serum concentrations of high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10), will be done at the study baseline and end of the trial. In addition, disease severity and disability will be assessed by DAS-28 and the HAQ-DI questionnaire, respectively.

Discussion

Diet is the leading environmental factor affecting the gut microbiota. A prebiotic-rich diet and probiotics might be beneficial in this regard. To the best of our knowledge, the effect of probiotic supplements on inflammation in these patients has widely been assessed; however, there is only one study that examined the effect of probiotic-containing food in these patients. Further studies are needed to investigate the effect of probiotic-containing foods on inflammatory markers and symptoms in patients with RA.

Trial registration

Iranian Registry of Clinical Trials IRCT20201120049449N1. Registered on 14 February 2021

The Microbiota in Systemic Lupus Erythematosus: An Update on the Potential Function of Probiotics

Systemic lupus erythematosus (SLE) is a kind of chronic diffuse connective tissue illness characterized by multisystem and multiorgan involvement, repeated recurrence and remission, and the presence of a large pool of autoantibodies in the body. Although the exact cause of SLE is not thoroughly revealed, accumulating evidence has manifested that intake of probiotics alters the composition of the gut microbiome, regulating the immunomodulatory and inflammatory response, which may be linked to the disease pathogenesis. Particularly, documented experiments demonstrated that SLE patients have remarkable changes in gut microbiota compared to healthy controls, indicating that the alteration of microbiota may be implicated in different phases of SLE. In this review, the alteration of microbiota in the development of SLE is summarized, and the mechanism of intestinal microbiota on the progression of immune and inflammatory responses in SLE is also discussed. Due to limited reports on the effects of probiotics supplementation in SLE patients, we emphasize advancements made in the last few years on the function and mechanisms of probiotics in the development of SLE animal models. Besides, we follow through literature to survey whether probiotics supplements can be an adjuvant therapy for comprehensive treatment of SLE. Research has indicated that intake of probiotics alters the composition of the gut microbiome, contributing to prevent the progression of SLE. Adjustment of the gut microbiome through probiotics supplementation seems to alleviate SLE symptoms and their cardiovascular and renal complications in animal models, marking this treatment as a potentially novel approach.

From Microbiome to Inflammation: The Key Drivers of Cervical Cancer

Cervical cancer is the third leading cause of cancer-related death worldwide. Microbes and hosts form a mutually beneficial symbiosis relationship, and various parts of the host body are microbial habitats. Microbes can trigger inflammation in certain parts of the host body, contributing to cervical cancer development. This article reviews the relationship between cervicovaginal microbes, inflammation and cervical cancer, and discusses the effect of some key cervical microbes on cervical cancer. Finally, probiotic therapy and immunotherapy are summarized.

Probiotics and synbiotics show clinical efficacy in treating gestational diabetes mellitus: A meta-analysis

BACKGROUND

This study performed a systematic and meta-analysis of randomized controlled trials (RCTs) to explore the efficacy of probiotic- and symbiotic-based supplements in the treatment of gestational diabetes mellitus (GDM).

METHODS

We performed a meta-analysis to evaluate the efficacy of probiotics/synbiotics in GDM treatment, following a systematic search in Web of Science, PubMed, Cochrane Library, and EBSCO databases for articles published up to July 2020.

RESULTS

In total, 12 RCTs comprising 894 participants, were analyzed. Compared to the placebo, patients administered with probiotic and synbiotic supplements benefited more with regards to glucose and lipid metabolism as well as anti-inflammation and antioxidant capacity including insulin of change (WMD: 3.57, 95%CI: -5.26, -1.88), very-low-density lipoprotein (VLDL) (WMD: -5.03, 95%CI: -8.26, -1.79), nitric oxide (NO) at the end of trial (WMD: 2.31, 95%CI: 0.91, 3.70), total antioxidant capacity (TAC) at the end of trial (SMD: 0.74, 95%CI: 0.21, 1.27), high-sensitivity C-reactive protein (hsCRP) at the end of trial (SMD: -1.23, 95%CI: -1.97, -0.49). Besides, probiotic and synbiotic supplements improved outcomes on fetal hyperbilirubinemia risk (RR: 0.26, 95%CI: 0.12, 0.55), fetal macrosomia risk (RR: 0.47, 95%CI: 0.27, 0.83) and newborn weight (SMD: -0.29, 95%CI: -0.50, -0.09).

CONCLUSIONS

Findings from this work demonstrate that probiotic/symbiotic-based interventions improve glucose and lipid metabolism, anti-inflammatory and antioxidant ability in diet-controlled GDM patients, and exert beneficial outcomes on fetal hyperbilirubinemia, fetal macrosomia, and newborn weight.

Versatile human in vitro triple coculture model coincubated with adhered gut microbes reproducibly mimics pro-inflammatory host-microbe interactions in the colon

The colonic epithelial barrier is vital to preserve gut and host health by maintaining the immune homeostasis between host and microbes. The mechanisms underlying beneficial or harmful host-microbe interactions are poorly understood and impossible to study in vivo given the limited accessibility and ethical constraints. Moreover, existing in vitro models lack the required cellular complexity for the routine, yet profound, analysis of the intricate interplay between different types of host and microbial cells. We developed and characterized a broadly applicable, easy-to-handle in vitro triple coculture model that combines chemically-induced macrophage-like, goblet and epithelial cells covered by a mucus layer, which can be coincubated with complex human-derived gut microbiota samples for 16 h. Comparison with a standard epithelial monolayer model revealed that triple cocultures produce thicker mucus layers, morphologically organize in a network and upon exposure to human-derived gut microbiota samples, respond via pro-inflammatory cytokine production. Both model systems, however, were not suffering from cytotoxic stress or different microbial loads, indicating that the obtained endpoints were caused by the imposed conditions. Addition of the probiotic Lactobacillus rhamnosus GG to assess its immunomodulating capacity in the triple coculture slightly suppressed pro-inflammatory cytokine responses, based on transcriptomic microarray analyses. TNF conditioning of the models prior to microbial exposure did not cause shifts in cytokines, suggesting a strong epithelial barrier in which TNF did not reach the basolateral side. To conclude, the triple coculture model is tolerable towards manipulations and allows to address mechanistic host-microbe research questions in a stable in vitro environment.

Effect of impaired T-cell receptor signaling on the gut microbiota and systemic autoimmunity

OBJECTIVE

T-cell receptor (TCR) signaling abnormalities and gut dysbiosis are thought to be involved in the development of systemic lupus erythematosus (SLE). However, it is not known whether these mechanisms are interrelated. This study explored the impact of defective TCR signaling on microbiota-driven immune responses and the consequent triggering of systemic autoimmunity.

METHODS

The responses of B6SKG mice harboring a mutation in the zeta-chain-associated protein kinase 70 in terms of spontaneous development of SLE were evaluated in specific-pathogen- and germ-free conditions. Gut microbiome was analyzed using 16S rRNA sequencing. Secretory immunoglobulin (Ig)A production in the gut and T follicular helper cells (Tfh) development in the spleen and Peyer's patches were analyzed. Interleukin (IL)-17-deficient mice and segmented filamentous bacteria (SFB)-specific TCR transgenic mice were used to examine the role of IL-17 and thymic selection.

RESULTS

SLE development by B6SKG mice was significantly more attenuated in germ free conditions than in specific -pathogen-free conditions. The gut microbiota in B6SKG mice was altered, which was associated with the expansion of SFB and consequent development of SLE by driving Thelper 17 (Th17)-cell differentiation, which was in turn blunted by IL-17 deficiency. Notably, although systemic Tfh development and autoantibody IgG response were enhanced, local gut Tfh and IgA responses were impaired. Moreover, experiments in SFB-specific TCR transgenic mice revealed that this differential response was caused by altered thymic selection of self- and microbiota-reactive TCR because of defective TCR signaling.

CONCLUSIONS

Defective TCR signaling alters the gut microbiota and promotes systemic autoimmunity by driving Th17-cell differentiation.

Probiotic Supplementation for Rheumatoid Arthritis: A Promising Adjuvant Therapy in the Gut Microbiome Era

Rheumatoid arthritis (RA) is a chronic immune-mediated inflammatory disease that ultimately leads to joint destruction and functional disability. Although the exact etiology of RA is not fully understood, it is well established that gut microbiota (GM) plays a vital role in the pathogenesis of RA, with accumulating evidence suggesting that gut dysbiosis induces a chronic inflammatory response that may be linked to disease development. Of interest, patients with RA have significant changes in the intestinal microbiota compared to healthy controls, and several studies have suggested the use of probiotics as a possible adjuvant therapy for RA. Benefits of probiotic supplementation were reported in animal models of arthritis and human studies, but the current evidence regarding the effect of probiotic supplementation in the management of RA remains insufficient to make definite recommendations. Several different strains of Lactobacillus and Bifidobacteria, as single species or in mixed culture, have been investigated, and some have demonstrated beneficial effects on disease activity in RA human subjects. As of now, L.casei probiotic bacteria seems to be the strongest candidate for application as adjuvant therapy for RA patients. In this review, we highlight the role of GM in the development and progression of RA and summarize the current knowledge on the use of probiotics as a potential adjuvant therapy for RA. We also review the proposed mechanisms whereby probiotics regulate inflammation. Finally, the role of fermented foods is discussed as a possible alternative to probiotic supplements since they have also been reported to have health benefits.

Alterations in mucosa-associated microbiota in the stomach of patients with gastric cancer

PURPOSE

The purpose of this study was to characterize alterations in mucosa-associated microbiota in different anatomical locations of the stomach during gastric cancer progression and to identify associations between Helicobacter pylori infection and gastric microbial changes in patients with gastric cancer.

METHODS

Twenty-five H. pylori negative subjects with chronic gastritis and thirty-four subjects with gastric cancer were recruited, including H. pylori negative and positive patients with tumors in the antrum and the corpus. Gastric mucosa-associated microbiota were determined by 16S ribosomal RNA gene sequencing using a 454 sequencing platform.

RESULTS

We found that individuals with chronic gastritis from three different anatomical sites exhibited different microbiota compositions, although the microbial alpha diversity, richness and beta diversity were similar. Compared to patients with chronic gastritis, the gastric microbiota compositions were significantly different at the order level in the antrum and the corpus of patients with gastric cancer, which was dependent on the H. pylori infection status. Microbial alpha diversity and species richness, however, were similar between chronic gastritis and gastric cancer cases and independent of H. pylori status. The microbial community structure in patients with gastric cancer was distinct from that in patients with chronic gastritis. In addition, we found that the presence of H. pylori markedly altered the structure in gastric corpus cancer, but only mildly affected the antrum.

CONCLUSION

Our data revealed distinct niche-specific microbiota alterations during the progression from gastritis to gastric cancer. These alterations may reflect adaptions of the microbiota to the diverse specific environmental habitats in the stomach, and may play an important, as yet undetermined, role in gastric carcinogenesis.

The Immunomodulatory Effect of the Gut Microbiota in Kidney Disease

The human gut microbiota is a complex cluster composed of 100 trillion microorganisms, which holds a symbiotic relationship with the host under normal circumstances. Intestinal flora can facilitate the treatment of human metabolic dysfunctions and interact with the intestinal tract, which could influence intestinal tolerance, immunity, and sensitivity to inflammation. In recent years, significant interests have evolved on the association of intestinal microbiota and kidney diseases within the academic circle. Abnormal changes in intestinal microbiota, known as dysbiosis, can affect the integrity of the intestinal barrier, resulting in the bacterial translocation, production, and accumulation of dysbiotic gut-derived metabolites, such as urea, indoxyl sulfate (IS), and p-cresyl sulfate (PCS). These processes lead to the abnormal activation of immune cells; overproduction of antibodies, immune complexes, and inflammatory factors; and inflammatory cell infiltration that can directly or indirectly cause damage to the renal parenchyma. The aim of this review is to summarize the role of intestinal flora in the development and progression of several renal diseases, such as lupus nephritis, chronic kidney disease, diabetic nephropathy, and renal ischemia-reperfusion injury. Further research on these mechanisms should provide insights into the therapeutic potential of regulating intestinal flora and intervening related molecular targets for the abovementioned nephropathy.

Alterations of the Skin and Gut Microbiome in Psoriasis and Psoriatic Arthritis

Numerous scientific studies in recent years have shown significant skin and gut dysbiosis among patients with psoriasis. A significant decrease in microbiome alpha-diversity (abundance of different bacterial taxa measured in one sample) as well as beta-diversity (microbial diversity in different samples) was noted in psoriasis skin. It has been proven that the representation of Cutibacterium, Burkholderia spp., and Lactobacilli is decreased and Corynebacterium kroppenstedii, Corynebacterium simulans, Neisseria spp., and Finegoldia spp. increased in the psoriasis skin in comparison to healthy skin. Alterations in the gut microbiome in psoriasis are similar to those observed in patients with inflammatory bowel disease. In those two diseases, the F. prausnitzii, Bifidobacterium spp., Lactobacillus spp., Parabacteroides and Coprobacillus were underrepresented, while the abundance of Salmonella sp., Campylobacter sp., Helicobacter sp., Escherichia coli, Alcaligenes sp., and Mycobacterium sp. was increased. Several research studies provided evidence for the significant influence of psoriasis treatments on the skin and gut microbiome and a positive influence of orally administered probiotics on the course of this dermatosis. Further research is needed to determine the influence of the microbiome on the development of inflammatory skin diseases. The changes in microbiome under psoriasis treatment can serve as a potential biomarker of positive response to the administered therapy.

Experiences and perceptions of patients with psoriatic arthritis participating in a trial of faecal microbiota transplantation: a nested qualitative study

OBJECTIVES

Patients' first-hand experiences of faecal microbiota transplantation (FMT) performed in a rheumatological care setting have yet to be elucidated. The objectives were to explore participants' perceptions of being part of an FMT trial thereby identifying potential trial participation effects and enlightening the patient perspective on the outlook for future FMT trials in rheumatic diseases.

DESIGN

In a qualitative study nested within a double-blind, randomised, placebo-controlled trial (RCT) testing FMT as a potential new antirheumatic treatment, semistructured telephone interviews were conducted following the trial participants' final 26-week visit. Qualitative researchers, who did not take part in the main trial, performed the interviews and the primary analysis. The experiences explored related to the conduct of the RCT and changes in the participants' everyday life. The analysis was carried out using a thematic approach.

SETTING

A Danish rheumatology university outpatient clinic with nationwide inclusion.

PARTICIPANTS

The study included 10 patients with psoriatic arthritis (PsA) who were unaware of their treatment allocation (FMT/sham transplantation) and completed the final 26-week trial visit.

RESULTS

Participation in the RCT influenced the patients' understanding of PsA and induced positive changes in their everyday life. Renewed hopes for the future in addition to a feeling of enhanced care contributed to significant trial participation effects. FMT was deemed a tolerable and safe treatment.

CONCLUSIONS

Discrepancies between the clinical and the research setting should be considered when discussing the clinical relevance of the results of the RCT. Overall, patients with PsA who have participated in an RCT testing FMT find the treatment acceptable and safe encouraging more research into the field of microbiota-targeted interventions in rheumatic diseases.

TRIAL REGISTRATION NUMBER

NCT03058900; Pre-results.

Nutrition and Rheumatoid Arthritis in the 'Omics' Era

Modern high-throughput 'omics' science tools (including genomics, transcriptomics, proteomics, metabolomics and microbiomics) are currently being applied to nutritional sciences to unravel the fundamental processes of health effects ascribed to particular nutrients in humans and to contribute to more precise nutritional advice. Diet and food components are key environmental factors that interact with the genome, transcriptome, proteome, metabolome and the microbiota, and this life-long interplay defines health and diseases state of the individual. Rheumatoid arthritis (RA) is a chronic autoimmune disease featured by a systemic immune-inflammatory response, in genetically susceptible individuals exposed to environmental triggers, including diet. In recent years increasing evidences suggested that nutritional factors and gut microbiome have a central role in RA risk and progression. The aim of this review is to summarize the main and most recent applications of 'omics' technologies in human nutrition and in RA research, examining the possible influences of some nutrients and nutritional patterns on RA pathogenesis, following a nutrigenomics approach. The opportunities and challenges of novel 'omics technologies' in the exploration of new avenues in RA and nutritional research to prevent and manage RA will be also discussed.

The RNA-binding protein tristetraprolin regulates RALDH2 expression by intestinal dendritic cells and controls local Treg homeostasis

AU-rich element (ARE)-mediated mRNA decay represents a key mechanism to avoid excessive production of inflammatory cytokines. Tristetraprolin (TTP, encoded by Zfp36) is a major ARE-binding protein, since Zfp36^-/- mice develop a complex multiorgan inflammatory syndrome that shares many features with spondyloarthritis. The role of TTP in intestinal homeostasis is not known. Herein, we show that Zfp36^-/- mice do not develop any histological signs of gut pathology. However, they display a clear increase in intestinal inflammatory markers and discrete alterations in microbiota composition. Importantly, oral antibiotic treatment reduced both local and systemic joint and skin inflammation. We further show that absence of overt intestinal pathology is associated with local expansion of regulatory T cells. We demonstrate that this is related to increased vitamin A metabolism by gut dendritic cells, and identify RALDH2 as a direct target of TTP. In conclusion, these data bring insights into the interplay between microbiota-dependent gut and systemic inflammation during immune-mediated disorders, such as spondyloarthritis.

Loss and gain of bone in spondyloarthritis: what drives these opposing clinical features?

The breadth of bone lesion types seen in spondyloarthritis is unprecedented in medicine and includes increased bone turnover, bone loss and fragility, osteitis, osteolysis and erosion, osteosclerosis, osteoproliferation of soft tissues adjacent to bone and spinal skeletal structure weakness. Remarkably, these effects can be present simultaneously in the same patient. The search for a potential unifying cause of effects on the skeleton necessarily focuses on inflammation arising from the dysregulation of immune response to microorganisms, particularly dysregulation of T_H17 lymphocytes, and the dysbiosis of established gut and other microbiota. The compelling notion that a common antecedent pathological mechanism affects existing bone and tissues with bone-forming potential (entheses), simultaneously with variable effect in the former but bone-forming in the latter, drives basic research forward and focuses our awareness on the effects on these bone mechanisms of the increasing portfolio of targeted immunotherapies used in the clinic.

Diet as a Modulator of Intestinal Microbiota in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic immune-driven inflammatory disease characterised by synovial inflammation, leading to progressive cartilage and bone destruction, impacting patients' functional capacity and quality of life. Patients with RA have significant differences in gut microbiota composition when compared to controls. Intestinal dysbiosis influences the intestinal barrier strength, integrity and function, and diet is considered the main environmental factor impacting gut microbiota. Over the last few years, researchers have focused on the influence of single components of the diet in the modulation of intestinal microbiota in RA rather than whole dietary patterns. In this review, we focus on how the Mediterranean diet (MD), a whole dietary pattern, could possibly act as an adjuvant therapeutic approach, modulating intestinal microbiota and intestinal barrier function in order to improve RA-related outcomes. We also review the potential effects of particular components of the MD, such as n-3 polyunsaturated fatty acids (PUFAs), polyphenols and fibre.

Regulating Gut Microbiome: Therapeutic Strategy for Rheumatoid Arthritis During Pregnancy and Lactation

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovial inflammation and bone destruction. Microbial infection is considered to be the most important inducement of RA. The pregnancy planning of women in childbearing age is seriously affected by the disease activity of RA. Gut microbiome, related to immunity and inflammatory response of the host. At present, emerging evidence suggested there are significant differences in the diversity and abundance of gut microbiome during pregnancy and lactation, which may be associated with the fluctuation of RA disease activity. Based on these research foundations, we pioneer the idea of regulating gut microbiome for the treatment of RA during pregnancy and lactation. In this review, we mainly introduce the potential treatment strategies for controlling the disease activity of RA based on gut microbiome during pregnancy and lactation. Besides, we also briefly generalize the effects of conventional anti-rheumatic drugs on gut microbiome, the effects of metabolic changes during pregnancy on gut microbiome, alteration of gut microbiome during pregnancy and lactation, and the effects of anti-rheumatic drugs commonly used during pregnancy and lactation on gut microbiome. These will provide a clear knowledge framework for researchers in immune-related diseases during pregnancy. Regulating gut microbiome may be a potential and effective treatment to control the disease activity of RA during pregnancy and lactation.

Gut Microbiome and Its Interaction with Immune System in Spondyloarthritis

Emerging evidence suggests there is a gut-joint axis in spondyloarthritis (SpA). In a study, subclinical gut inflammation occurred in nearly 50% of SpA. Chronic gut inflammation also correlated with disease activity in SpA. Trillions of microorganisms reside in the human gut and interact with the human immune system. Dysbiosis affects gut immune homeostasis and triggers different autoimmune diseases including SpA. The absence of arthritis in HLA-B27 germ-free mice and the development of arthritis after the introduction of commensal bacteria to HLA-B27 germ-free mice proved to be the important role of gut bacteria in shaping SpA, other than the genetic factor. The recent advance in gene sequencing technology promotes the identification of microorganisms. In this review, we highlighted current evidence supporting the link between gut and axial SpA (axSpA). We also summarized available findings of gut microbiota and its interaction with the immune system in axSpA. Future research may explore the way to modulate gut microorganisms in axSpA and bring gut microbiome discoveries towards application.

Hsp65-Producing Lactococcocus lactis Prevents Antigen-Induced Arthritis in Mice

Oral tolerance is the physiological process that enables the immune system to differentiate between harmless dietary and microbiota antigens from pathogen derived antigens. It develops at the mucosal surfaces and can result in local and systemic regulatory and anti-inflammatory effects. Translation of these benefits to the clinical practice faces limitations involving specificity and doses of antigen as well as regimens of feeding. To circumvent these problems, we developed a recombinant Hsp65 delivered by the acid lactic bacteria Lactococcus lactis NCDO 2118 directy in the intestinal mucosa. Hsp65 is a ubiquitous protein overexpressed in inflamed tissues and capable of inducing immunoregulatory mechanisms. L. lactis has probiotic properties and is commonly and safely used in dairy products. In this study, we showed that continuous delivery of HSP65 in the gut mucosa by L. lactis is a potent tolerogenic stimulus inducing regulatory CD4⁺LAP⁺ T cells that prevented collagen-induced and methylated bovine serum albumin-induced arthritis in mice. Clinical and histological signs of arthritis were inhibited as well as levels of inflammatory cytokines such as IL-17 and IFN-γ, serum titers of anti-collagen antibodies and rheumatoid factor. Oral administration of L. lactis induced alterations in microbiota composition toward an increased abundance of anaerobic bacteria such as Bifidobacterium and Lactobacillus. Tolerance to HSP65 and arthritis prevention induced by the recombinant L. lactis was associated with increase in IL-10 production by B cells and it was dependent on LAP⁺ T cells, IL-10 and TLR2 signaling. Therefore, HSP65-producing treatment induced effective tolerance and prevented arthritis development suggesting it can be used as a therapeutic tool for autoimmune diseases.

Potential Associations Among Alteration of Salivary miRNAs, Saliva Microbiome Structure, and Cognitive Impairments in Autistic Children

Recent evidence has demonstrated that salivary molecules, as well as bacterial populations, can be perturbed by several pathological conditions, including neuro-psychiatric diseases. This relationship between brain functionality and saliva composition could be exploited to unveil new pathological mechanisms of elusive diseases, such as Autistic Spectrum Disorder (ASD). We performed a combined approach of miRNA expression profiling by NanoString technology, followed by validation experiments in qPCR, and 16S rRNA microbiome analysis on saliva from 53 ASD and 27 neurologically unaffected control (NUC) children. MiR-29a-3p and miR-141-3p were upregulated, while miR-16-5p, let-7b-5p, and miR-451a were downregulated in ASD compared to NUCs. Microbiome analysis on the same subjects revealed that Rothia, Filifactor, Actinobacillus, Weeksellaceae, Ralstonia, Pasteurellaceae, and Aggregatibacter increased their abundance in ASD patients, while Tannerella, Moryella and TM7-3 decreased. Variations of both miRNAs and microbes were statistically associated to different neuropsychological scores related to anomalies in social interaction and communication. Among miRNA/bacteria associations, the most relevant was the negative correlation between salivary miR-141-3p expression and Tannerella abundance. MiRNA and microbiome dysregulations found in the saliva of ASD children are potentially associated with cognitive impairments of the subjects. Furthermore, a potential cross-talking between circulating miRNAs and resident bacteria could occur in saliva of ASD.

Impact of infections in autoimmune rheumatic diseases and pregnancy

PURPOSE OF REVIEW

To provide an update about the impact of infections in autoimmune rheumatic diseases (ARDs), from the analysis of the role of infections in pregnant women without ARDs, to the identification of maternal-fetal infections and their role in the maternal-fetal outcome of women with ARDs.

RECENT FINDINGS

Recent studies indicate that patients with ARDs and pregnancy are also susceptible to presenting infections of varying degrees, including serious infections, which contribute to the morbidity and mortality observed in pregnancy and postpartum of these patients.Any type of infectious agent will interact with a hormonal, immunological and metabolic environments modified by ARD, treatments, and by the changes inherent in pregnancy. Therefore, infections in the pregnancy of patients with ARDs should be considered as a risk factor for an unfavorable maternal-fetal outcome.

SUMMARY

The recognition of infections in the pregnancy of ARDs as a risk factor is the first step to prevent, identify, and treat them in a timely manner, and thus contribute to the favorable course of pregnancy in these patients. Patients with ARDs and major organ involvement, use of high doses of steroids, immunosuppressant and biological therapies, adolescence, and obesity are populations susceptible to developing infections.

Gut microbiota in children with juvenile idiopathic arthritis: characteristics, biomarker identification, and usefulness in clinical prediction

Background

Recent studies have suggested that the gut microbiota is altered in children with juvenile idiopathic arthritis (JIA). However, age, sex, and body mass index (BMI) were not matched in the previous studies, and the results are inconsistent. We conducted an age-, sex-, and BMI-matched cross-sectional study to characterize the gut microbiota in children with JIA, and evaluate its potential in clinical prediction.

Methods

A total of 40 patients with JIA and 42 healthy controls, ranging from 1 to 16 years, were enrolled in this study. Fecal samples were collected for 16S rDNA sequencing. The data were analyzed using QIIME software and R packages. Specifically, the random forest model was used to identify biomarkers, and the receiver operating characteristic curve and the decision curve analysis were used to evaluate model performance.

Results

A total of 39 fecal samples from patients with JIA, and 42 fecal samples from healthy controls were sequenced successfully. The Chao 1 and Shannon–Wiener index in the JIA group were significantly lower than those in the control group, and the Bray-Curtis dissimilarity also differed significantly between the two groups. The relative abundance of 4 genera, Anaerostipes, Dialister, Lachnospira, and Roseburia, decreased significantly in the JIA group compared to those in the control group. The 4 genera included microbes that produce short-chain fatty acids (SCFAs) and were negatively correlated with some rheumatic indices. Moreover, 12 genera were identified as potential biomarkers by using the nested cross-validation function of the random forest. A random forest model constructed using these genera was able to differentiate the patients with JIA from the healthy controls, and the area under the receiver operating characteristic curve was 0.7975. The decision curve analysis indicated that the model had usefulness in clinical practice.

Conclusions

The gut microbiota in patients with JIA is altered and characterized by a decreased abundance of 4 SCFA-producing genera. The decreases in the 4 genera correlated with more serious clinical indices. Twelve genera could be used as biomarkers and predictors in clinical practice.

Trial registration

The study is registered online at the Chinese Clinical Trial Registry on 11 May 2018 (registration number: ChiCTR1800016110).