Metabolomic Biomarker Candidates for Skeletal Muscle Loss in the Collagen-Induced Arthritis (CIA) Model.

There is no consensus for diagnosis or treatment of RA muscle loss. We aimed to investigate metabolites in arthritic mice urine as biomarkers of muscle loss. DBA1/J mice comprised collagen-induced arthritis (CIA) and control (CO) groups. Urine samples were collected at 0, 18, 35, 45, 55, and 65 days of disease and subjected to nuclear magnetic resonance spectroscopy. Metabolites were identified using Chenomx and Birmingham Metabolite libraries. The statistical model used principal component analysis, partial least-squares discriminant analysis, and partial least-squares regression analysis. Linear regression and Fisher's exact test via the MetaboAnalyst website were performed (VIP-score). Nearly 100 identified metabolites had CIA vs. CO and disease time-dependent differences (p < 0.05). Twenty-eight metabolites were muscle-associated: carnosine (VIPs 2.8 × 102) and succinyl acetone (VIPs 1.0 × 10) showed high importance in CIA vs. CO models at day 65; CIA pair analysis showed histidine (VIPs 1.2 × 102) days 55 vs. 65, histamine (VIPs 1.1 × 102) days 55 vs. 65, and L-methionine (VIPs 1.1 × 102) days 0 vs. 18. Carnosine was fatigue- (0.039) related, creatine was food intake- (-0.177) and body weight- (-0.039) related, and both metabolites were clinical score- (0.093; 0.050) and paw edema- (0.125; 0.026) related. Therefore, muscle metabolic alterations were detected in arthritic mice urine, enabling further validation in RA patient's urine, targeting prognosis, diagnosis, and monitoring of RA-mediated muscle loss.

Cachexia in patients with rheumatoid arthritis: a cohort study.

BACKGROUND: Rheumatoid arthritis (RA) is an inflammatory disease that leads to altered body composition. The loss of lean mass with a preservation or increase in fat mass has been termed rheumatoid cachexia (RC), to contrast with classic cachexia, which is characterized by severe weight loss. There are limited data on the prevalence and progression of cachexia in RA over time, as well as on associated factors. Our aim was to determine the prevalence of cachexia and to determine associations with potential factors. METHODS: This prospective cohort study recruited consecutively patients diagnosed with RA and followed for 1 year. The assessments were performed: clinical features, body composition, and physical function. RC and classic cachexia were assessed by several established diagnostic criteria. The pairwise Student's t test, Chi-square test, and GEE were performed (accepted at p ≤ 0.05). RESULTS: Of 90 patients recruited, 81 completed the study. Most patients were women (88.9%), and the mean age was 56.5 ± 7.3 years. At baseline, the median DAS28-CRP was 3.0 (IQR, 1.0-3.0), 13.3-30.0% of the included patients had RC, while none met criteria for classic cachexia. The prevalence of cachexia did not change after 12 months. Disease activity status and treatment with biologic disease-modifying antirheumatic drugs were significantly associated with changes on body composition and physical function (p < 0.05). CONCLUSIONS: In this cohort, RC was common, while classic cachexia was absent. Disease activity and use of biologic therapies were associated with changes on body composition and physical function, underscoring the importance of aiming for remission when treating RA.

Prevalence of rheumatoid cachexia in rheumatoid arthritis: a systematic review and meta-analysis.

BACKGROUND: Low muscle mass occurs in patients with rheumatoid arthritis without weight loss; this condition is referred as rheumatoid cachexia. The aim of the current study was to perform a systematic review with meta-analysis to determine the rheumatoid cachexia prevalence. METHODS: A systematic review with meta-analysis of observational studies published in English, between 1994 and 2016, was conducted using MEDLINE (via PubMed) and other relevant sources. Search strategies were based on pre-defined keywords and medical subject headings. The methodological quality of included studies was assessed using the Newcastle-Ottawa Scale. Meta-analysis was used to estimate the prevalence, and because studies reported different methods and criteria to estimate body composition and prevalence of rheumatoid cachexia, subgroup analyses were performed. Meta-regression adjusted for the 28-joint disease activity score and disease duration (years) was performed (significance level at P ≤ 0.05). RESULTS: Of 136 full articles (one duplicate publication) screened for inclusion in the study, eight were included. The estimated overall prevalence of rheumatoid cachexia was 19% [95% confidence interval (CI) 07-33%]. This prevalence was 29% (95% CI 15-46%) when body composition was measured by dual-energy X-ray absorptiometry. When the diagnostic criteria were fat-free mass index below the 10th percentile and fat mass index above the 25th percentile, rheumatoid cachexia prevalence was 32% (95% CI 14-52%). The 28-joint disease activity score and disease duration had no influence on the estimated prevalence of rheumatoid cachexia (P > 0.05). Most studies were rated as having moderate methodological quality. CONCLUSIONS: Meta-analysis showed a prevalence of rheumatoid cachexia of 15-32%, according to different criteria, demonstrating that this condition is a frequent comorbidity of rheumatoid arthritis. To better understand its clinical impact, more studies using standardized definitions and prospective evaluations are urgently needed.

Collagen-induced arthritis as an animal model of rheumatoid cachexia.

BACKGROUND: Rheumatoid arthritis is characterized by chronic polyarticular synovitis and presents systemic changes that impact quality of life, such as impaired muscle function, seen in up to 66% of the patients. This can progress to severely debilitating state known as rheumatoid cachexia-without loss of fat mass and body weight-for which there is little consensus in terms of diagnosis or treatment. This study aims to evaluate whether the collagen-induced arthritis (CIA) animal model also develops clinical and functional features characteristic of rheumatoid cachexia. METHODS: Male DBA1/J mice were randomly divided into 2 groups: healthy animals (CO, n = 11) and CIA animals (n = 13). The clinical score and edema size, animal weight and food intake, free exploratory locomotion, grip strength, and endurance exercise performance were tested 0, 18, 35, 45, 55, and 65 days after disease induction. After euthanasia, several organs, visceral and brown fat, and muscles were dissected and weighed. Muscles were used to assess myofiber diameter. Ankle joint was used to assess arthritis severity by histological score. Statistical analysis were performed using one-way and two-way analyses of variance followed by Tukey's and Bonferroni's test or t-test of Pearson and statistical difference were assumed for a P value under 0.05. RESULTS: The CIA had significantly higher arthritis scores and larger hind paw edema volumes than CO. The CIA had decreased endurance exercise performance total time (fatigue; 23, 22, 24, and 21% at 35, 45, 55, and 65 days, respectively), grip strength (27, 55, 63, 60, and 66% at 25, 35, 45, 55, and 65 days, respectively), free locomotion (43, 57, 59, and 66% at 35, 45, 55, and 65 days, respectively), and tibialis anterior and gastrocnemius muscle weight (25 and 24%, respectively) compared with CO. Sarcoplasmic ratios were also reduced in CIA (TA: 23 and GA: 22% less sarcoplasmic ratio), confirming the atrophy of skeletal muscle mass in these animals than in CO. Myofiber diameter was also reduced 45% in TA and 41% in GA in CIA when compared with the CO. Visceral and brown fat were lighter in CIA (54 and 39%, respectively) than CO group. CONCLUSIONS: The CIA model is a valid experimental model for rheumatoid cachexia given that the clinical changes observed were similar to those described in patients with rheumatoid arthritis.

Effect of pegylated phosphatidylserine-containing liposomes in experimental chronic arthritis.

BACKGROUND: Phosphatidylserine-containing liposomes (PSL) have been shown to reduce inflammation in experimental models of acute arthritis, by mimicking the apoptotic process. The aim of this study was to evaluate the effect of pegylated PSL (PEG-PSL) on chronic inflammation of collagen induced arthritis (CIA) in DBA/1J mice. METHODS: CIA was induced in 24 DBA/1J mice (n = 6/group), which were divided into control (0.9 % saline) or treated with PEG-PSL (5, 10 and 15 mg/kg/day, subcutaneously for 20 days). Clinical score, limb histology and measurement of cytokines in knee joints of animals by ELISA and cytometric bead array (CBA) were evaluated. The in vitro study employed macrophage cultures stimulated with 100 ng/ml of LPS plus 10 ng/ml of PMA and treated with 100 µM PEG-PSL. RESULTS: Resolution of the disease in vivo and the inflammatory process in vitro were not observed. PEG-PSL, in doses of 10 and 15 mg/kg, were not shown to reduce the score of the disease in animals, whereas with the dose of 5 mg/kg, the animals did not show the advanced stage of the disease when compared to the controls. The PEG- PSL 5, 10 and 15 mg/kg treatment groups did not show significant reduction of TNF-α, IL-1ß, IL-6, IL-2 and IFN-γ when compared to the controls. Disease incidence and animal weights were not affected by treatment. Regarding the paw histology, PEG-PSL did not yield any reductions in the infiltrating mononuclear, synovial hyperplasia, extension of pannus formation, synovial fibrosis, erosion of cartilage, bone erosion or cartilage degradation. The concentration of 100 µM of PEG-PSL has not been shown to reduce inflammation induced by LPS/PMA in the in vitro study. Treated groups did not show any reduction in inflammatory cytokines in the knee joints of animals affected by the disease compared to the control, although there were higher concentrations of TGF-ß1 in all experimental groups. CONCLUSION: The experimental model showed an expression of severe arthritis after the booster. TGF-ß1 as well other pro inflammatory cytokines were presented in high concentrations in all groups. PEG-PSL had no impact on the clinical score, the histopathology from tibial-tarsal joints or the production of cytokines in the knee joints. Other alternatives such as dosage, route of administration, and as an adjunct to a drug already on the market, should be evaluated to support the use of PEG-PSL as a new therapeutic tool in inflammatory diseases.

Temporal development of muscle atrophy in murine model of arthritis is related to disease severity.

BACKGROUND: Rheumatoid arthritis (RA) is an inflammatory autoimmune disease of unknown etiology, affecting mainly the joint but also other tissues. RA patients usually present weakness and muscle atrophy, nonarticular manifestations of the disease. Although causing great impact, the understanding of muscle atrophy, its development, and the mechanisms involved is still very limited. The objective of this study is to evaluate the development of muscle atrophy in skeletal muscle of a murine model of arthritis. METHODS: The experimental murine model of collagen-induced arthritis (CIA) was used. DBA/1J mice were randomly divided into three groups: control (CO, n = 25), sham arthritis (SA, n = 25), and arthritis (CIA, n = 28), analyzed in different time points: 25, 35, and 45 days after the induction of arthritis. The arthritis development was followed by clinical scores and hind paw edema three times a week. The spontaneous exploratory locomotion and weight were evaluated weekly. In all time points, serum was collected before the death of the animals for cytokine analysis, and myofiber cross-sectional areas (CSA) of gastrocnemius (GA) and tibialis anterior (TA) skeletal muscles were evaluated. RESULTS: The clinical parameters of arthritis progressively increased in CIA in all experimental times, demonstrating the greatest difference from other groups at 45 days after induction (clinical score: CO, 00 ± 00; SA, 1.00 ± 0.14; CIA, 3.28 ± 0.41 p > 0.05). The CIA animals had lower weights during all the experimentation periods with a difference of 6 % from CO at 45 days (p > 0.05). CIA animals also demonstrated progressive decrease in distance walked, with a reduction of 54 % in 35 and 74 % at 45 days. Cytokine analysis identified significant increase in IL-6 serum levels in CIA than CO and SA in all experimental times. CSA of the myofiber of GA and TA was decreased 26 and 31 % (p > 0.05) in CIA in 45 days after the induction of disease, respectively. There was significant and inverse correlation between the disease clinical score and myofiber CSA in 45 days (GA: r = -0.71; p = 0.021). CONCLUSION: Our results point to a progressive development of muscle wasting, with premature onset arthritis. These observations are relevant to understand the development of muscle loss, as well as for the design of future studies trying to understand the mechanisms involved in muscle wasting. As far as we are concerned, this is the first study to evaluate the relation between disease score and muscle atrophy in a model of arthritis.