Brief report: Assessment of mucosal barrier integrity using serological biomarkers in preclinical stages of rheumatoid arthritis

The role of gut flora-driven Th cell responses in preclinical rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disorder with an immune pathogenesis that evolves over decades. Preclinical RA (PreRA) represents a dynamic immune phase preceding clinical RA, marked by the loss of autoimmune tolerance, the appearance of tissue-invasive effector T cells, and the production of autoantibodies (such as antibodies against citrullinated proteins and rheumatoid factors). Extensive research has demonstrated that gut microbiota influence mucosal T-cell responses, driving the progression of PreRA through multiple mechanisms, including altered intestinal permeability, gene-environment interactions, bacterial antigenic specificity, molecular mimicry, and metabolite production. Environmental risk factors such as smoking, hormonal changes, and high-sodium (Na) diets, may contribute to RA pathogenesis via the gut microbiome. The next challenge in RA research lies in developing therapeutic strategies to intervene during the asymptomatic autoimmune phase, where dietary adjustments, natural compounds, probiotics, and other approaches could effectively modulate gut flora to prevent or delay RA onset.

Associations between intestinal fatty-acid binding protein and clinical and metabolic characteristics of depression

INTRODUCTION

The topic of increased intestinal permeability is associated with disruption of the intestinal barrier, leading to the "leaky gut" syndrome. Depressive disorders often coexist with abdominal obesity, metabolic syndrome, or its components and complications. Intestinal permeability has been proven to relate to all of the above.

METHODS

In this cross-sectional study, we aimed to assess the "leaky gut" blood biomarker - intestinal fatty acid-binding protein (I-FABP) - in 114 adult patients diagnosed with depressive disorders depending on abdominal obesity comorbidity, depression, anxiety, and stress level, or antidepressant use. The corrected p-value was set at 0.02. We analyzed patients' mental state, diet, anthropometric parameters, metabolic laboratory markers and I-FABP.

RESULTS

There was no difference in circulating I-FABP levels between obese and non-obese patients with depressive disorders (p = 0.648). Similarly, I-FABP levels were not different in patients with different emotional symptoms severity (p = 0.829 for self-assessed depression, p = 0.164 for anxiety, and p = 0.543 for stress). But, I-FABP levels differed significantly between patients treated and not treated with antidepressants (p = 0.011). In general linear model analysis treatment with antidepressants, anxiety severity level, their interaction, along with smoking status, drinks intake, and using dietary supplements were shown to significantly explain I-FABP variance (p < 0.001, R2adj = 0.261).

CONCLUSIONS

Comorbid obesity did not increase intestinal permeability circulating marker, I-FABP, in the population of patients with depressive disorders. Treatment with antidepressants may be connected to higher I-FABP levels. Using dietary supplements, drinks intake, smoking status, or anxiety level may serve as explanatory factors.

Patterns of antibiotic resistance genes and virulence factor genes in the gut microbiome of patients with osteoarthritis and rheumatoid arthritis

Background

The gut microbiome compositions of osteoarthritis (OA) and rheumatoid arthritis (RA) patients have been revealed; however, the functional genomics, particularly antibiotic resistance genes (ARGs) and virulence factor genes (VFGs), have not yet been explored.

Methods

We used gut metagenomic data to elucidate the distribution of ARGs and VFGs. Building on these differences in gut microbiome, we developed a diagnostic model using a random forest classifier based on ARG and VFG abundances.

Results

Our results indicated that both OA and RA patients exhibit significantly higher alpha diversity in ARGs, as measured by observed genes, the Shannon index, and the Simpson index, compared to healthy controls. However, this increased diversity is not significantly different between OA and RA patients. In contrast, VFGs showed higher diversity in RA patients than in healthy individuals, which was not as pronounced in OA patients. An analysis of the top 20 ARGs and VFGs revealed a largely similar composition between the three groups, with notable exceptions of certain genes that were uniquely enriched in either OA or RA patients. This suggests unique microbial patterns associated with each condition. Our beta diversity analysis further demonstrated distinct distributions of ARG and VFG profiles across the three groups, with several genes significantly enriched in both OA and RA patients, indicating potential markers for these diseases. The model achieved high accuracy (74.7-83.6%) when distinguishing both OA and RA from healthy controls using ARG profiles and substantial accuracy using VFG profiles.

Conclusion

These results support the potential of ARGs and VFGs as reliable biomarkers for diagnosing OA and RA.

Menopause and Estrogen Associations With Gut Barrier, Microbial Translocation, and Immune Activation Biomarkers in Women With and Without HIV

OBJECTIVES

Estrogens may protect the gut barrier and reduce microbial translocation and immune activation, which are prevalent in HIV infection. We investigated relationships of the menopausal transition and estrogens with gut barrier, microbial translocation, and immune activation biomarkers in women with and without HIV.

DESIGN

Longitudinal and cross-sectional studies nested in the Women's Interagency HIV Study.

METHODS

Intestinal fatty acid binding protein, lipopolysaccharide binding protein, and soluble CD14 (sCD14) levels were measured in serum from 77 women (43 with HIV) before, during, and after the menopausal transition (∼6 measures per woman over ∼13 years). A separate cross-sectional analysis was conducted among 72 postmenopausal women with HIV with these biomarkers and serum estrogens.

RESULTS

Women in the longitudinal analysis were a median age of 43 years at baseline. In piecewise, linear, mixed-effects models with cutpoints 2 years before and after the final menstrual period to delineate the menopausal transition, sCD14 levels increased over time during the menopausal transition (Beta [95% CI]: 38 [12 to 64] ng/mL/yr, P = 0.004), followed by a decrease posttransition (-46 [-75 to -18], P = 0.001), with the piecewise model providing a better fit than a linear model (P = 0.0006). In stratified analyses, these results were only apparent in women with HIV. In cross-sectional analyses, among women with HIV, free estradiol inversely correlated with sCD14 levels (r = -0.26, P = 0.03). Lipopolysaccharide binding protein and intestinal fatty acid binding protein levels did not appear related to the menopausal transition and estrogen levels.

CONCLUSIONS

Women with HIV may experience heightened innate immune activation during menopause, possibly related to the depletion of estrogens.

Gut microbiome and intestinal inflammation in preclinical stages of rheumatoid arthritis

BACKGROUND

Faecal Prevotellaceae, and other microbes, have been associated with rheumatoid arthritis (RA) and preclinical RA. We have performed a quantitative microbiome profiling study in preclinical stages of RA.

METHODS

First-degree relatives of patients with RA (RA-FDRs) from the SCREEN-RA cohort were categorised into four groups: controls, healthy asymptomatic RA-FDRs; high genetic risk, asymptomatic RA-FDRs with two copies of the shared epitope; autoimmunity, asymptomatic RA-FDRs with RA-associated autoimmunity; and symptomatic, clinically suspect arthralgias or untreated new-onset RA.Faecal samples were collected and frozen. 16S sequencing was performed, processed with DADA2 pipeline and Silva database. Cell counts (cytometry) and faecal calprotectin (enzyme-linked immunosorbent assay, ELISA) were also obtained. Microbial community analyses were conducted using non-parametric tests, such as permutational multivariate analysis of variance (PERMANOVA), Wilcoxon and Kruskal-Wallis, or Aldex2.

RESULTS

A total of 371 individuals were included and categorised according to their preclinical stage of the disease. Groups had similar age, gender and body mass index. We found no significant differences in the quantitative microbiome profiles by preclinical stages (PERMANOVA, R2=0.00798, p=0.56) and, in particular, no group differences in Prevotellaceae abundance. Results were similar when using relative microbiome profiling data (PERMANOVA, R2=0.0073, p=0.83) or Aldex2 on 16S sequence counts. Regarding faecal calprotectin, we found no differences between groups (p=0.3).

CONCLUSIONS

We could not identify microbiome profiles associated with preclinical stages of RA. Only in a subgroup of individuals with the most pronounced phenotypes did we modestly retrieve the previously reported associations.

Assessment of Intestinal Permeability and Inflammation Bio-Markers in Patients with Rheumatoid Arthritis

Increased intestinal permeability and inflammation, both fueled by dysbiosis, appear to contribute to rheumatoid arthritis (RA) pathogenesis. This single-center pilot study aimed to investigate zonulin, a marker of intestinal permeability, and calprotectin, a marker of intestinal inflammation, measured in serum and fecal samples of RA patients using commercially available kits. We also analyzed plasma lipopolysaccharide (LPS) levels, a marker of intestinal permeability and inflammation. Furthermore, univariate, and multivariate regression analyses were carried out to determine whether or not there were associations of zonulin and calprotectin with LPS, BMI, gender, age, RA-specific parameters, fiber intake, and short-chain fatty acids in the gut. Serum zonulin levels were more likely to be abnormal with a longer disease duration and fecal zonulin levels were inversely associated with age. A strong association between fecal and serum calprotectin and between fecal calprotectin and LPS were found in males, but not in females, independent of other biomarkers, suggesting that fecal calprotectin may be a more specific biomarker than serum calprotectin is of intestinal inflammation in RA. Since this was a proof-of-principle study without a healthy control group, further research is needed to validate fecal and serum zonulin as valid biomarkers of RA in comparison with other promising biomarkers.