Etiology Of Rheumatoid Arthritis Research Articles

Vitamin K homologs as potential biomarkers for disease activity in patients with rheumatoid arthritis

The aim of this study was to evaluate the possible role of vitamin K homologs as potential biomarkers for disease activity in patients with rheumatoid arthritis (RA). In this study, 42 patients with RA and 40 healthy controls were enrolled. Serum levels of vitamin K homologs were measured using a high-performance liquid chromatography-fluorescence method. Different biochemical and clinical markers for disease activity were measured and correlated with serum levels of vitamin K homologs. There were no significant differences between RA patients and healthy subjects in demographic data. Patients with RA showed significantly higher levels of biochemical markers compared with healthy subjects (p<0.001). These markers included rheumatoid factor (RF), anticyclic citrullinated polypeptide (anti-CCP), undercarboxylated osteocalcin (ucOC), matrix metalloproteinase (MMP-3), C-reactive protein (CRP), and disease activity score assessing 28 joints with erythrocyte sedimentation rate (DAS28-ESR). In addition, serum levels of vitamin K homologs were reduced in RA patients, and the levels of menaquinone-4 (MK-4) and menaquinone-7 (MK-7) were moderately to strongly inversely correlated with the clinical articular features in RA patients, whereas phylloquinone (PK) levels were weakly correlated. Serum levels of MK-4, MK-7 and PK were strongly inversely correlated with ucOC, MMP-3 and DAS28-ESR in RA patients. In contrast, serum levels of MK-4, MK-7 and PK were weakly correlated with CRP, RF and anti-CCP. These results suggest that serum levels of vitamin K homologs may be considered as potential biomarkers for disease activity. In addition, the results confirm the role of vitamin K deficiency in the etiology of RA.

Changes in peripheral blood lymphocyte subsets during arthritis development in arthralgia patients

BackgroundMultiple lymphocyte subsets like T and B cells have been connected to joint infiltration and inflammation in rheumatoid arthritis (RA). Identification of leucocyte subsets that are dysregulated in arthritis development could provide insight into the aetiology of RA. This study aimed to investigate the composition of the peripheral blood components, i.e. CD14+ monocytes, CD4+ and CD8+ T lymphocytes (CD3+), CD80+, C-X-C chemokine receptor 3 (CXCR3)+ and CD27+ B lymphocytes (CD19+), CD16+CD56+CD3− natural killer (NK) cells and activated CD56+CD3+ T cells, for association with arthritis development in patients with arthralgia.MethodsPeripheral blood was collected from 89 patients with early RA (disease duration <6 months), 37 healthy controls (HC) and 113 patients with arthralgia (22 developed arthritis within ≤1 year, 18 developed arthritis after >1 year and 73 did not develop arthritis). Absolute numbers of monocytes and lymphocyte subsets in whole heparinized blood were determined with flow cytometry using quantification beads in combination with fluorescent labelled antibodies for T cells, B cells, monocytes, NK cells and activated T cells.ResultsIn patients with early RA, significant decreases in numbers of (activated) T cells, CD80+ and memory B cells and a trend towards smaller numbers of CD8+ T cells was observed compared to HC. Similar differences were seen in patients with arthralgia who developed or did not develop arthritis (non-converters), with significantly decreased CD8+ T cells and memory B cells. Patients with arthralgia who developed arthritis were split into groups that developed arthritis within 1 year (early converters) or after 1 year (late converters). Late converters had a significantly decreased number of CD8+ T cells compared to non-converters; early converters had a decreased number of memory B cells. Longitudinal analysis of converters showed a significant relative increase in CD80+ B cells towards the conversion time point compared to 24 months prior to conversion.ConclusionsThis study revealed that patients with arthralgia who develop arthritis demonstrate a change in cellular immune parameters apparent in the periphery, starting with a decrease in cytotoxic T cells 24 months prior to arthritis development, followed by a decrease in the number of memory B cells 12 months prior to disease onset.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-016-1102-2) contains supplementary material, which is available to authorized users.

Update on Therapeutic Approaches for Rheumatoid Arthritis.

Rheumatoid arthritis is a common chronic inflammatory and destructive arthropathy that consumes considerable personal, social and economic costs. It consists of a syndrome of pain, stiffness and symmetrical inflammation of the synovial membrane (synovitis) of freely moveable joints such as the knee (diarthrodial joints). Although the etiology of rheumatoid arthritis is unclear, the disease is characterized by inflammation of the synovial lining of diarthrodial joints, high synovial proliferation and an influx of inflammatory cells, macrophages and lymphocytes through angiogenic blood vessels. Diseasemodifying antirheumatic drugs slow disease progression and can induce disease remission in some patients. Methotrexate is the first line therapy, but if patients become intolerant to this drug, biologic agents should be used. The development of biological substances for the treatment of rheumatic conditions has been accompanied by ongoing health economic discussions regarding the implementation of these highly effective, but accordingly, highly priced drugs are the standard treatment guidelines of rheumatic diseases. In this way, more efficient strategies have to be identified. Despite numerous reviews in rheumatoid arthritis in the last years, this area is in constant development and updates are an urgent need to incorporate new advances in rheumatoid arthritis research. This review highlights the immunopathogenesis rationale for the current therapeutic strategies in rheumatoid arthritis.

Associations of Smoking and Age With Inflammatory Joint Signs Among Unaffected First-Degree Relatives of Rheumatoid Arthritis Patients: Results From Studies of the Etiology of Rheumatoid Arthritis.

To examine whether genetic, environmental, and serologic rheumatoid arthritis (RA) risk factors are associated with inflammatory joint signs in a cohort of first-degree relatives (FDRs) of RA patients. We evaluated RA risk factors and inflammatory joint signs in a prospective cohort of FDRs without RA in the Studies of the Etiology of RA. Genetic factors included 5 HLA-DRB1 shared epitope alleles and 45 RA-associated single-nucleotide polymorphisms; loci were combined using genetic risk scores weighted by RA risk. Environmental factors (smoking, body mass index, education, and parity) and RA-related autoantibodies were assessed at baseline. Physical examination was performed at baseline and 2-year follow-up, by observers who were blinded with regard to autoantibody status, to assess inflammatory joint signs as tender or swollen joints at sites typical for RA. Logistic regression was performed to evaluate associations of genetic, environmental, and serologic factors with inflammatory joint signs. We analyzed 966 non-Hispanic white FDRs at baseline and 262 at 2-year follow-up after excluding those with inflammatory joint signs at baseline. The mean ± SD age was 47.2 ± 15.5 years, 71% were female, and 55% were shared epitope positive. Smoking >10 pack-years was associated with inflammatory joint signs at baseline (odds ratio [OR] 1.89 [95% confidence interval (95% CI) 1.26-2.82]) and at 2 years (OR 2.66 [95% CI 1.01-7.03]), compared to never smokers. There was a significant interaction between smoking and age with regard to risk of inflammatory joint signs (P = 0.02). FDRs younger than 50 years with >10 pack-years had the highest risk of inflammatory joint signs (OR 4.39 [95% CI 2.22-8.66], compared to never smokers younger than 50 years). In a high-risk cohort of FDRs, smoking and age were associated with both prevalent and incident inflammatory joint signs at sites typical for RA. Further prospective investigations of the factors affecting the transitions between preclinical RA phases are warranted.

Single Cell Chemical Cytometry of Akt Activity in Rheumatoid Arthritis and Normal Fibroblast-like Synoviocytes in Response to Tumor Necrosis Factor α.

The etiology of rheumatoid arthritis (RA) is poorly understood, and 30% of patients are unresponsive to established treatments targeting tumor necrosis factor α (TNFα). Akt kinase is implicated in TNFα signaling and may act as a barometer of patient responses to biologic therapies. Fluorescent peptide sensors and chemical cytometry were employed to directly measure Akt activity as well as proteolytic activity in individual fibroblast-like synoviocytes (FLS) from RA and normal subjects. The specificity of the peptide reporter was evaluated and shown to be a valid measure of Akt activity in single cells. The effect of TNFα treatment on Akt activity was highly heterogeneous between normal and RA subjects, which was not observable in bulk analyses. In 2 RA subjects, a bimodal distribution of Akt activity was observed, primarily due to a subpopulation (21.7%: RA Subject 5; 23.8%: RA Subject 6) of cells in which >60% of the reporter was phosphorylated. These subjects also possessed statistically elevated proteolytic cleavage of the reporter relative to normal subjects, suggesting heterogeneity in Akt and protease activity that may play a role in the RA-affected joint. We expect that chemical cytometry studies pairing peptide reporters with capillary electrophoresis will provide valuable data regarding aberrant kinase activity from small samples of clinical interest.

Omega-3 fatty acids are associated with a lower prevalence of autoantibodies in shared epitope-positive subjects at risk for rheumatoid arthritis

ObjectivesPreviously, we found that omega-3 fatty acids (n-3 FAs) were inversely associated with anti-cyclic citrullinated peptide (anti-CCP) positivity in participants at risk for future rheumatoid arthritis (RA). We investigated whether...

Evaluation of tool-like receptor-2 and 4 and interleukin-6 gene expressions in Turkish rheumatoid arthritis patients.

Rheumatoid arthritis (RA) is a progressive inflammatory disease. Although the etiology and pathogenesis of RA are not known well, genetic and environmental factors are proposed to initiate an autoimmune process. We aimed to investigate mRNA expression levels of Toll-like receptor-2 (TLR-2), TLR-4, and interleukin-6 (IL-6) genes in RA disease. This study was conducted with 50 patients who were diagnosed with RA according to the American College of Rheumatology classification criteria for RA and 50 age-matched healthy control individuals who did not have any joint diseases and autoimmune diseases. We collected whole blood from all participants and analyzed expression of TLR-2, TLR-4, and IL-6 genes at mRNA level using real-time qPCR. TLR-2 expression was detected to increase 3.8-fold and IL-6 expression was detected to increase 6.8-fold in RA patients compared to healthy controls. No difference was found between patient and control groups with regard to TLR-4 expression. Overexpression of TLR-2 and IL-6 may be responsible for RA pathogenesis. Inhibition of both TLR and IL signaling pathways may prevent joint inflammation and destruction.

Family history of rheumatoid arthritis: an old concept with new developments

Family history of rheumatoid arthritis (RA) is a proxy for an individual's genetic and, in part, environmental risk of developing RA, and is a well-recognized predictor of disease onset. Although family history of RA is an old concept, the degree of familial aggregation of RA, whether it differs by age, sex, or serology, and what value it has for clinical decisions once a diagnosis of RA has been made remain unclear. New data have been emerging in parallel to substantial progress made in genetic association studies. In this Review, we describe the various ways that familial aggregation has been measured, and how the findings from these studies, whether they are based on twins, cohorts of first-degree relatives, or genetic data, correspond to each other and aid understanding of the aetiology of RA. In addition, we review the potential usefulness of family history of RA from a clinical point of view, demonstrating that, in the era of big data and genomics, family history still has a role in directing clinical decision-making and research.

Molecular Insight into Gut Microbiota and Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is a systemic, inflammatory, and autoimmune disorder. Gut microbiota play an important role in the etiology of RA. With the considerable progress made in next-generation sequencing techniques, the identified gut microbiota difference between RA patients and healthy individuals provides an updated overview of the association between gut microbiota and RA. We reviewed the reported correlation and underlying molecular mechanisms among gut microbiota, the immune system, and RA. It has become known that gut microbiota contribute to the pathogenesis of RA via multiple molecular mechanisms. The progressive understanding of the dynamic interaction between gut microbiota and their host will help in establishing a highly individualized management for each RA patient, and achieve a better efficacy in clinical practice, or even discovering new drugs for RA.

The Roles of Cigarette Smoking and the Lung in the Transitions Between Phases of Preclinical Rheumatoid Arthritis.

While the etiology of rheumatoid arthritis (RA) remains to be fully elucidated, recent research has advanced the understanding of RA pathogenesis to the point where clinical trials for RA prevention are underway. The current paradigm for RA pathogenesis is that individuals progress through distinct preclinical phases prior to the onset of clinically apparent RA. These preclinical RA phases consist of genetic risk, local inflammation, presence of RA-related autoantibodies, asymptomatic systemic inflammation, and early non-specific symptoms prior to clinical seropositive RA. Epidemiologic studies have been important in forming hypotheses related to the biology occurring in preclinical RA. Specifically, studies associating cigarette smoking with overall RA risk as well as transitions between phases of preclinical RA were vital in helping to establish the lung as a potential important initiating site in the pathogenesis of seropositive RA. Herein, we review the epidemiology associating smoking with transitions in preclinical phases of RA as well as the recent literature supporting the lung as a critical site in RA pathogenesis.

Abstract P131: Associations Between Joint Symptoms and Prospective Changes in Physical Activity in First-degree Relatives of Rheumatoid Arthritis (RA) Patients

Background: CVD is accelerated in RA, and risk of CVD death is 50% higher in RA patients. Physical activity (PA) mitigates increased CVD risk, but RA patients typically have less PA. It is not known whether PA declines prior to RA onset, or whether joint symptoms (sxs) contribute to PA decline. We sought to determine whether RA-related joint sxs were associated with PA over time in first-degree relatives (FDRs) of RA patients, a population at increased risk for future RA. Methods: In the Studies of the Etiology of RA (SERA), we evaluated associations between presence of joint sxs and hours of PA in 878 FDRs; of whom, 376 had ≥2 visits. A physician confirmed joint swelling; participants self-reported stiffness and pain in the wrist, elbow, or any MCP, PIP, or MTP joints. Hours sleeping, sitting, and performing slight, moderate, or heavy activity during a typical 24-hour day were obtained through questionnaire, weighted to reflect metabolic expenditure, and calculated as follows: PA = (1.0*h sleep + 1.1*h sedentary + 1.5*h slight + 2.4*h moderate + 5.0*h heavy ). Linear mixed models were used to evaluate associations between joint sxs and change in PA over time, adjusting for age, sex, race, BMI, smoking, and positivity for RA-related autoantibodies Results: Mean baseline age was 50±16 years. 74% were female, 78% were White, 7% had joint swelling, 15% had joint stiffness, and 24% had joint pain. Average PA was 37±7. At baseline, PA was higher in FDRs with joint stiffness (B=1.27±0.64, p=0.05) and joint pain (B=1.43±0.54, p=0.01), and lower in FDRs with joint swelling (B=-1.50±0.91, p=0.10). Adjusting for baseline PA, baseline joint swelling, stiffness, and pain were not significantly associated with changes in PA. However, change in joint swelling was associated with increased PA; and changes in joint stiffness and pain were associated with decreased PA. (Table) Conclusion: Joint sxs may not predict future PA, but PA may be lower at the time joint sxs occur. Clinicians should address joint sxs as part of their PA intervention in CVD prevention.

Antibodies to Porphyromonas gingivalis Indicate Interaction Between Oral Infection, Smoking, and Risk Genes in Rheumatoid Arthritis Etiology.

To investigate the role of the periodontal pathogen Porphyromonas gingivalis in the etiology of rheumatoid arthritis (RA) by analyzing the antibody response to the P gingivalis virulence factor arginine gingipain type B (RgpB) in relation to anti-citrullinated protein antibodies (ACPAs), smoking, and HLA-DRB1 shared epitope (SE) alleles in patients with periodontitis, patients with RA, and controls. Anti-RgpB IgG was measured by enzyme-linked immunosorbent assay in 65 periodontitis patients and 59 controls without periodontitis, and in 1,974 RA patients and 377 controls without RA from the Swedish population-based case-control Epidemiological Investigation of Rheumatoid Arthritis (EIRA) study. Autoantibody status, smoking habits, and genetic data were retrieved from the EIRA database. Differences in antibody levels were examined using the Mann-Whitney U test. Unconditional logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals (95% CIs) for the association of anti-RgpB IgG with different subsets of RA patients. Anti-RgpB antibody levels were significantly elevated in periodontitis patients compared to controls without periodontitis, in RA patients compared to controls without RA, and in ACPA-positive RA patients compared to ACPA-negative RA patients. There was a significant association between anti-RgpB IgG and RA (OR 2.96 [95% CI 2.00, 4.37]), which was even stronger than the association between smoking and RA (OR 1.37 [95% CI 1.07, 1.74]), and in ACPA-positive RA there were interactions between anti-RgpB antibodies and both smoking and the HLA-DRB1 SE. Our study suggests that the previously reported link between periodontitis and RA could be accounted for by P gingivalis infection, and we conclude that P gingivalis is a credible candidate for triggering and/or driving autoimmunity and autoimmune disease in a subset of RA patients.

The Mechanisms Underlying Chronic Inflammation in Rheumatoid Arthritis from the Perspective of the Epigenetic Landscape.

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that is characterized by synovial hyperplasia and progressive joint destruction. The activation of RA synovial fibroblasts (SFs), also called fibroblast-like synoviocytes (FLS), contributes significantly to perpetuation of the disease. Genetic and environmental factors have been reported to be involved in the etiology of RA but are insufficient to explain it. In recent years, accumulating results have shown the potential role of epigenetic mechanisms, including histone modifications, DNA methylation, and microRNAs, in the development of RA. Epigenetic mechanisms regulate chromatin state and gene transcription without any change in DNA sequence, resulting in the alteration of phenotypes in several cell types, especially RASFs. Epigenetic changes possibly provide RASFs with an activated phenotype. In this paper, we review the roles of epigenetic mechanisms relevant for the progression of RA.

Effects of Wutou Decoction on DNA Methylation and Histone Modifications in Rats with Collagen-Induced Arthritis

Background. Wutou decoction (WTD) has been wildly applied in the treatment of rheumatoid arthritis and experimental arthritis in rats for many years. Epigenetic deregulation is associated with the aetiology of rheumatoid arthritis; however, the effects of WTD on epigenetic changes are unclear. This study is set to explore the effects of WTD on DNA methylation and histone modifications in rats with collagen-induced arthritis (CIA). Methods. The CIA model was established by the stimulation of collagen and adjuvant. The knee synovium was stained with hematoxylin and eosin. The DNA methyltransferase 1 (DNMT1) and methylated CpG binding domain 2 (MBD2) expression of peripheral blood mononuclear cells (PBMCs) were determined by Real-Time PCR. The global DNA histone H3-K4/H3-K27 methylation and total histones H3 and H4 acetylation of PBMCs were detected. Results. Our data demonstrated that the DNMT1 mRNA expression was significantly lowered in group WTD compared to that in group CIA (P < 0.05). The DNA methylation level was significantly reduced in group WTD compared to that in group CIA (P < 0.05). Moreover, H3 acetylation of PBMCs was overexpressed in WTD compared with CIA (P < 0.05). Conclusions. WTD may modulate DNA methylation and histone modifications, functioning as anti-inflammatory potential.

Contribution of Peptide Backbone to Anti-Citrullinated Peptide Antibody Reactivity.

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases, affecting approximately 1–2% of the world population. One of the characteristic features of RA is the presence of autoantibodies. Especially the highly specific anti-citrullinated peptide antibodies (ACPAs), which have been found in up to 70% of RA patients’ sera, have received much attention. Several citrullinated proteins are associated with RA, suggesting that ACPAs may react with different sequence patterns, separating them from traditional antibodies, whose reactivity usually is specific towards a single target. As ACPAs have been suggested to be involved in the development of RA, knowledge about these antibodies may be crucial. In this study, we examined the influence of peptide backbone for ACPA reactivity in immunoassays. The antibodies were found to be reactive with a central Cit-Gly motif being essential for ACPA reactivity and to be cross-reactive between the selected citrullinated peptides. The remaining amino acids within the citrullinated peptides were found to be of less importance for antibody reactivity. Moreover, these findings indicated that the Cit-Gly motif in combination with peptide backbone is essential for antibody reactivity. Based on these findings it was speculated that any amino acid sequence, which brings the peptide into a properly folded structure for antibody recognition is sufficient for antibody reactivity. These findings are in accordance with the current hypothesis that structural homology rather than sequence homology are favored between citrullinated epitopes. These findings are important in relation to clarifying the etiology of RA and to determine the nature of ACPAs, e.g. why some Cit-Gly-containing sequences are not targeted by ACPAs.

Genetic factors of rheumatoid arthritis

Rheumatoid arthritis(RA)is one of common autoimmune diseases. As with other complex disorders, recent genome-wide association studies(GWASs)have greatly contributed to our understanding of RA etiology. In this review, the genetic configuration of RA as revealed through GWASs is described. In addition, I discuss the pathologic mechanisms of RA as suggested by the findings of genetic and functional studies of individual RA-associated genes, and the potential use of genetic information for novel drug discovery.

Assessments of Immunomodulatory and Inflammatory effects against Induction of Entamoeba histolytica (HM1 IMS strain) crude extract Antigen in Complete Freund’s Adjuvant Induced Rheumatoid Arthritis Female Wistar Rats

Today it is well known about mechanisms of cell communication, how the cells that mediate immune response and tissue injury accumulate in tissues but the aetiology of rheumatoid arthritis (RA) is still unknown. This study was to evaluate immunomodulatory effects of crude Entamoeba histolytica (HM1 IMS strain) antigen in complete freund's adjuvant female wistar rats by studying the alterations in humoral and cell mediated immune responses and also the inflammatory effects by evaluating the changes in body weight, paw thickness, biochemical, serological, interleukin-6 (IL-6), IL-10 and tumor necrosis factor-α (TNF-α) and histopathology activities. Animals were randomly divided into six groups (n=6). CFA was induced in arthritic, drug and AA+CFA group whereas, 0.5ml amoebic antigen was induced subplantal in AA group while 0.5ml dose of amoebic antigen was given orally to AA+CFA group for 7-28th days. Indomethacin was used as a standard drug. Effects of amoebic antigen were associated with increased paw thickness and decreased body weight when compared to healthy control showed a significant difference. Oral administration of amoebic antigen has showed increased severe symptoms of arthritis in AA+CFA on comparison to healthy control rats. Significant increase in serum level of IL-6 and α TNF were found in AA group followed by AA+CFA group whereas, decrease in concentration of IL-10 was appear in AA+CFA group on comparison to arthritic and healthy control group (P<0.05). Histopathology of AA group showed severe signs of necrotic and degenerative changes on comparison to healthy control group. Thus the results demonstrated that E. histolytica alone or in combination with CFA increased bone damage, with alterations in antioxidant level in liver and kidney tissue homogenates as well as showed immunomodulatory arthritogenic properties which may contribute and raise joint inflammation.

High serum cholesterol predicts rheumatoid arthritis in women, but not in men: a prospective study.

IntroductionEnvironmental exposures, including smoking, hormone-related factors, and metabolic factors, have been implicated in the etiology of rheumatoid arthritis (RA). A previous study has indicated that blood lipid levels may influence the development of RA. The objective of this study was to investigate the impact of serum total cholesterol and triglycerides on the risk of RA in a prospective study.MethodsAmong participants in a large population-based health survey (n = 33,346), individuals who subsequently developed RA were identified by linkage to four different registers and a structured review of the medical records. In a nested case-control study, with controls, matched for age, sex, and year of inclusion, from the health survey database, the relation between serum lipids (levels of total cholesterol and triglycerides) and future RA development was examined.ResultsIn total, 290 individuals (151 men and 139 women) whose RA was diagnosed a median of 12 years (range of 1–28) after inclusion in the health survey were compared with 1160 controls. Women with a diagnosis of RA during the follow-up had higher total cholesterol levels at baseline compared with controls: odds ratio (OR) 1.54 per standard deviation; 95 % confidence interval (CI) 1.22–1.94. This association remained statistically significant in multivariate models adjusted for smoking and a history of early menopause and in analyses stratified by rheumatoid factor status and time to RA diagnosis. Total cholesterol had no significant impact on the risk of RA in men (OR 1.03; 95 % CI 0.83–1.26). Triglycerides did not predict RA in men or women.ConclusionsA high total cholesterol was a risk factor for RA in women but not in men. This suggests that sex-specific exposures modify the impact of lipids on the risk of RA. Hormone-related metabolic pathways may contribute to RA development.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-015-0804-1) contains supplementary material, which is available to authorized users.

Determining Pathways to Improvements in Fatigue in Rheumatoid Arthritis: Results From the British Society for Rheumatology Biologics Register for Rheumatoid Arthritis.

There is debate as to the role of inflammatory disease activity in the etiology of rheumatoid arthritis (RA)-related fatigue. We undertook this study to determine the relationship of fatigue to disease activity by examining pathways associated with change in fatigue in subjects starting anti-tumor necrosis factor (anti-TNF) therapy for the first time. Participants who had been recruited to the British Society for Rheumatology Biologics Register for RA provided information on fatigue (Short Form 36 [SF-36] vitality scale) and other health status variables at the start of anti-TNF therapy and 6 months later. The Disease Activity Score in 28 joints (DAS28) and inflammation (erythrocyte sedimentation rate [ESR]/C-reactive protein [CRP] level) were also reported. A path analysis model comprising changes in fatigue, pain, disease activity, disability, and mental health, along with effects of sex and a history of depression, was used to examine those with high levels of fatigue at baseline (score of ≤12.5 units on the SF-36 vitality scale). The DAS28 was substituted for ESR/CRP to delineate the specific role of inflammation. With a total of 2,652 participants, we identified a well-fitting model (χ2 = 0.18, P = 0.98) accounting for 40% of the variance in fatigue change. There was no direct pathway from change in inflammation to change in fatigue; instead, significant pathways to change in fatigue were observed from changes in disease activity, pain, mental health, and disability, along with effects of sex and a history of depression. A total of 82% of the effect of change in disease activity was indirect, of which ∼50% was mediated through a change in pain. Improvements in fatigue do not appear to be driven by inflammatory disease activity; instead, they appear to result indirectly from improvements in pain. Additional significant pathways through disability and mental health suggest potentially modifiable factors that could be targeted to improve clinically important levels of fatigue.

RHEUMATOID ARTHRITIS: LABORATORY MODELS OF THE DISEASE

The establishment and application of animal models represent effective tools for research in rheumatoid arthritis (RA) pathogenesis. Animal models that replicate various mechanisms reflecting all aspects of RA, including early RA pathology, have provided important insights into studying etiology and pathogenetic mechanisms of RA in humans. This review article was compiled in order to give an introduction to the current state of RA models. Application of these experimental disorders for testing potential therapeutic approaches will help to make better predictions for drug efficiency in human RA