Objective: Regulatory interleukin‐10 (IL‐10)–producing B cells (B10 cells) have been shown to prevent and cure collagen‐induced arthritis in mice. In humans, very little is known about B10 cells in rheumatoid arthritis (RA). Several B cell subsets, such as CD24^highCD38^high, CD24^highCD27+, and CD5+ B cells, were suggested to be precursors of B10 cells. We aimed to analyze these B cell subsets and B10 cells in RA patients and healthy controls.Methods: B10 cells were generated from peripheral blood mononuclear cells stimulated for 24 hours with CpG and for 4 hours with phorbol 12‐myristate 13‐acetate/ionomycin/brefeldin A. Intracellular B cell IL‐10 was assessed by flow cytometry. Thirty‐one controls and 99 RA patients were included.Results: After multiple adjustments, levels of CD24^highCD38^high, CD24^highCD27+, and CD5+ B cells were found to be similar in RA patients and controls. Levels of B10 cells were lower in RA patients than in controls, especially in patients with RA of ≤5 years' duration. Levels of B10 cells correlated inversely with the Disease Activity Score in 28 joints. This was more pronounced in patients with RA of ≤5 years' duration, in whom B10 cells also correlated inversely with C‐reactive protein levels. Moreover, B10 cells correlated inversely with rheumatoid factor levels. CD24^highCD38^high and CD24^highCD27+ B cells induced more Treg cells than did CD24^low B cells in controls but not in RA patients.Conclusion: The ability of B cells to produce IL‐10 was altered in RA, and this impairment influenced disease activity, biologic inflammation, and autoantibody levels, especially in patients with RA of ≤5 years' duration. This strongly suggests a role of B10 cells in RA initiation.

Autoimmune diseases are characterized by a breakdown of immune tolerance partly due to environmental factors. The short-chain fatty acid acetate, derived mostly from gut microbial fermentation of dietary fiber, promotes antiinflammatory Tregs and protects mice from type 1 diabetes, colitis, and allergies. Here, we show that the effects of acetate extend to another important immune subset involved in tolerance, the IL-10–producing regulatory B cells (B10 cells). Acetate directly promoted B10 cell differentiation from mouse B1a cells both in vivo and in vitro. These effects were linked to metabolic changes through the increased production of acetyl-coenzyme A, which fueled the TCA cycle and promoted posttranslational lysine acetylation. Acetate also promoted B10 cells from human blood cells through similar mechanisms. Finally, we identified that dietary fiber supplementation in healthy individuals was associated with increased blood-derived B10 cells. Direct delivery of acetate or indirect delivery via diets or bacteria that produce acetate might be a promising approach to restore B10 cells in noncommunicable diseases.

Objective.: Obesity and overweight are increasing conditions. Adipose tissue with proinflammatory properties could be involved in rheumatoid arthritis (RA) activity and radiographic progression. This study aims to investigate the influence of overweight and obesity on RA activity and severity.Methods.: We conducted a systematic review and metaanalysis to assess the association of body mass index (BMI) categories with the Disease Activity Score in 28 joints (DAS28), functional disability [Health Assessment Questionnaire (HAQ)], and radiographic joint damage in patients with RA. We searched Medline through PubMed, EMBASE, and the Cochrane Database of Systematic Reviews for all studies assessing DAS28, HAQ, or/and radiographic damage according to predefined BMI groups.Results.: Among the 737 citations retrieved, 58 articles met the inclusion criteria and 7 were included in the metaanalysis. DAS28 was higher in obese (BMI > 30 kg/m²) than non-obese (BMI ≤ 30 kg/m²) patients (mean difference 0.14, 95% CI 0.01–0.27, p = 0.04, I² = 0%). HAQ score was also higher among obese patients (mean difference 0.10, 95% CI 0.01–0.19, p = 0.03, I² = 0%). Radiographic joint damage was negatively associated with obesity (standardized mean difference −0.15, 95% CI −0.29 to −0.02, p = 0.03, I² = 38%).Conclusion.: Obesity in RA is associated with increased DAS28 and HAQ score and with lower radiographic joint damage. These associations mainly result from an increase of subjective components of the DAS28 (total joint count and global health assessment) in obese patients. Conflicting results were reported concerning inflammation markers (C-reactive protein and erythrocyte sedimentation rate).

Overweight and obesity are increasing worldwide and now reach about one-third of the world's population. Obesity also involves patients with inflammatory arthritis. Knowing the impact of obesity on rheumatic diseases (rheumatoid arthritis, ankylosing spondylitis and psoriatic arthritis) is thus an important issue. This article first reviews the epidemiological and clinical data available on obesity in inflammatory rheumatic diseases, that is, its impact on incident disease, disease characteristics and the therapeutic response. The second part of this review gives an overview of the factors potentially involved in the specifics of inflammatory arthritis in patients with obesity, such as limitations in the clinical assessment, diet, microbiota and adipokines.

This article presents the 1st set of dietary recommendations of the French Society for Rheumatology for patients suffering from chronic inflammatory rheumatic diseases (IRD) made by a working group consisting of 12 rheumatology experts, 3 physician nutrition specialists, 1 internal medicine specialist, 1 registered dietician and 3 representatives from patient associations. This group relied on a systematic literature review and on expert opinions, while taking into consideration not only the joint effects of diet in IRD but also the extra-articular ones. Eight general principles and nine recommendations were established. The general principles emphasize that nutritional advice is not a substitute for pharmacological treatment of IRD and that it is an integral part of the patients' overall care, which could help the patient actively participate in their care. The recommendations propose supporting weight loss in subjects who are overweight or obese, a Mediterranean-type diet and supplementation in polyunsaturated fatty acids, mainly omega-3. Conversely, gluten-free diets (in the absence of celiac disease), vegetarian/vegan diets, fasting and elimination of dairy products should not be proposed. Supplementation with vitamins or trace elements is not indicated for controlling chronic IRD activity, while the use of probiotics or spices is not recommended given the limited or disparate data.