NMR-Based Metabolomics Revealed the Underlying Inflammatory Pathology in Reactive Arthritis Synovial Joints

Reactive arthritis (ReA) is an aseptic synovitis condition that often develops 2-4 weeks after a distant (extra-articular) infection with Chlamydia, Salmonella, Shigella, Campylobacter, and Yersinia species. The metabolic changes in the synovial fluid (SF) may serve as indicative markers to both improve the diagnostic accuracy and understand the underlying inflammatory pathology of ReA. With this aim, the metabolic profiles of SF collected from ReA (n = 58) and non-ReA, i.e., rheumatoid arthritis (RA, n = 21) and osteoarthritis (OA, n = 20) patients, respectively, were measured using NMR spectroscopy and compared using orthogonal partial least-squares discriminant analysis (OPLS-DA). The discriminatory metabolic features were further evaluated for their diagnostic potential using the receiver operating characteristic (ROC) curve analysis. Compared to RA, two (alanine and carnitine), and compared to OA, six (NAG, glutamate, glycerol, isoleucine, alanine, and glucose) metabolic features were identified as diagnostic biomarkers. We further demonstrated the impact of ReA synovitis condition on the serum metabolic profiles through performing a correlation analysis. The Pearson rank coefficient (r) was estimated for 38 metabolites (profiled in both SF and serum samples obtained in pair from ReA patients) and was found significantly positive for 71% of the metabolites (r ranging from 0.17 to 0.87).

Active Ingredients and Anti-Arthritic Mechanisms of Ba-Wei-Long-Zuan Granule Revealed by 1 H-NMR-Based Metabolomics Combined with Network Pharmacology Analysis

Ba-Wei-Long-Zuan granule (BWLZ) is a traditional herbal preparation. It has been widely used for the treatment of rheumatoid arthritis (RA). However, its active ingredients and mechanisms of action are still unclear. The present study aims to reveal the active compounds and anti-arthritic mechanisms of BWLZ against collagen-induced arthritis (CIA) by using ¹ H-NMR-based metabolomics, molecular docking and network pharmacology methods. After 30 days of administration, BWLZ could effectively improve the metabolic disorders in CIA rats. The anti-arthritic effect of BWLZ was related to its restoration of 16 disturbed serum metabolites. Molecular docking and network analysis showed that 20 compounds present in BWLZ could act on multiple targets. Among them, coclaurine and hesperidin showed the highest hit rates for target proteins related to both metabolic regulation and RA, indicating that these two compounds might be potential active ingredients of BWLZ. Moreover, pathway enrichment analysis suggested that the anti-arthritic mechanisms of BWLZ might be attributed to its network regulation of several biological processes, such as steroid hormone biosynthesis, mTOR signaling pathway, alanine, aspartate and glutamate metabolism, and synthesis and degradation of ketone bodies. These results provide further evidence for the anti-arthritic properties of BWLZ and are beneficial for its quality control and clinical application. The potential targets and biological processes found in this study may provide valuable information for further studying the molecular mechanisms of BWLZ against RA. In addition, our work provides new insights for revealing the active ingredients and regulatory mechanisms of complex herbal preparations.

Investigation of Efficacy Enhancing and Toxicity Reducing Mechanism of Combination of Aconiti Lateralis Radix Praeparata and Paeoniae Radix Alba in Adjuvant-Induced Arthritis Rats by Metabolomics

Combination of Aconiti Lateralis Radix Praeparata (FZ) and Paeoniae Radix Alba (BS) shows a significant effect in rheumatoid arthritis (RA). This study aimed to investigate the efficacy enhancing and toxicity reducing mechanism of combination of them in adjuvant-induced arthritis (AIA) rats by metabolomics. Rats were randomly divided into seven groups, including A (healthy control), B (model control), C1 (therapy group), C2 (efficacy enhancing group), D1 (toxicity group), and D2 (toxicity reducing group), and dexamethasone group was used as positive control. The plasma biochemical indexes showed that therapeutic dose of lipid-soluble alkaloids of FZ could significantly inhibit the concentrations of IL-1β, TNF-α, and IFN-γ in AIA rats, and combination with total glucosides of peony could further reduce the concentration of IL-1β. Then, UPLC-LTQ/Orbitrap MS with untargeted metabolomics was performed to identify the possible metabolites and pathways. Through multivariate data analysis of therapeutic dose groups (A vs. B vs. C1 vs. C2) and multivariate data analysis of toxic dose groups (A vs. B vs. D1 vs. D2), 10 and 7 biomarkers were identified based on biomarker analysis, respectively. After inducing AIA model, the plasma contents of spermidine, vanillylmandelic acid, catechol, and linoleate were increased significantly, and the contents of citric acid, L-tyrosine, L-phenylalanine, leucine, L-tryptophan, and uridine 5'-monophosphate (UMP) were decreased significantly. High dose of lipid-soluble alkaloids of FZ could increase the plasma contents of L-lysine, L-arginine, and deoxycholic acid, while the plasma contents of UMP, carnitine, N-formylanthranilic acid, and adenosine were decreased significantly. The pathway analysis indicated that therapeutic dose of lipid-soluble alkaloids of FZ could regulate energy and amino acid metabolic disorders in AIA rats. However, toxic dose could cause bile acid, fat, amino acid, and energy metabolic disorders. And combination with total glucosides of peony could enhance the therapeutic effects and attenuate the toxicity induced by lipid-soluble alkaloids of FZ.

NMR-Based Serum Metabolomics Revealed Distinctive Metabolic Patterns in Reactive Arthritis Compared with Rheumatoid Arthritis

Reactive arthritis (ReA) is a member of seronegative spondyloarthropathy (SSA), which involves an acute/subacute onset of asymmetrical lower limb joint inflammation weeks after a genitourinary/gastrointestinal infection. The diagnosis is clinical because it is difficult to culture the microbes from synovial fluid. Arthritis patients with a similar clinical picture but lapsed history of an immediate preceding infection that do not fulfill the diagnostic criteria of other members of SSA, such as ankylosing spondylitis, psoriatic arthritis, and arthritis associated with inflammatory bowel disease, are labeled as peripheral undifferentiated spondyloarthropathy (uSpA). Both ReA and uSpA patients show a strong association with class I major histocompatibility complex allele, HLA-B27, and a clear association with an infectious trigger; however, the disease mechanism is far from clear. Because the clinical picture is largely dominated by rheumatoid-arthritis (RA)-like features including elevated levels of inflammatory markers (such as ESR, CRP, etc.), these overlapping symptoms often confound the clinical diagnosis and represent a clinical dilemma, making treatment choice more generalized. Therefore, there is a compelling need to identify biomarkers that can support the diagnosis of ReA/uSpA. In the present study, we performed NMR-based serum metabolomics analysis and demonstrated that ReA/uSpA patients are clearly distinguishable from controls and further that these patients can also be distinguished from the RA patients based on the metabolic profiles, with high sensitivity and specificity. The discriminatory metabolites were further subjected to area under receiver operating characteristic curve analysis, which led to the identification of four metabolic entities (i.e., valine, leucine, arginine/lysine, and phenylalanine) that could differentiate ReA/uSpA from RA.

The Association Between Musculoskeletal Pain and Circulating Ornithine: A Population-Based Study

Objective

Based on several previous clinical studies, we hypothesized that ornithine levels are different among subjects with persistent musculoskeletal pain compared with other subjects in the population.

Design

The study sample consisted of 221 adults with nonpersistent pain, 76 with persistent pain, and 61 with no pain. Concentrations of glutamic acid, ornithine, citrulline, arginine, proline, and spermidine were analyzed using a mass spectrometer.

Setting

Lapinlahti municipality in Finland.

Results

For the subjects with no pain, nonpersistent pain, and persistent pain, the ornithine concentrations for men were 85.3 µmol/L (SD = 28.9 µmol/L), 98.9 µmol/L (SD = 37.8 µmol/L), and 102.1 µmol/L (SD = 37.1 µmol/L; P  = 0.033), respectively. The corresponding concentrations for women were 82.8 µmol/L (SD = 25.2 µmol/L), 83.7 µmol/L (SD = 27.8 µmol/L), and 103.2 µmol/L (SD = 34.9 µmol/L; P  = 0.0031). There were no significant differences between the pain groups for any of the other investigated amino acids. Relative sex-specific ornithine concentration adjusted for age, glomerular filtration rate, smoking, body mass index, physical activity, and depressive symptoms was associated with pain ( P  = 0.025), the ornithine level being higher in the persistent pain group than in the no pain ( P  = 0.006) and nonpersistent pain ( P  = 0.032) groups.

Conclusion

Ornithine levels are elevated in general population subjects with persistent pain.

Role of amino acids in rheumatoid arthritis studied by metabolomics

BACKGROUND

Rheumatoid arthritis (RA) is a complex, chronic autoimmune disease characterized by various inflammatory symptoms, including joint swelling, joint pain, and both structural and functional joint damage. The most commonly used animal model for studying RA is mice with collagen-induced arthritis (CIA); the wide use of this model is due primarily to many similarities with RA in human patients. Metabolomics is used increasingly in biological studies for diagnosing disease and for predicting and evaluating drug interventions, as a large number of disease-associated metabolites can be analyzed and interpreted from a biological perspective.

AIM

To profile free amino acids and their biogenic metabolites in CIA mice plasma.

METHOD

Ultra-high-performance liquid chromatography/tandem mass spectrometry coupled with multiple reaction monitoring (MRM) was used for metabolomics study.

RESULTS

Profile of 45 amine metabolites, including free amino acids and their biogenic metabolites in plasma was obtained from CIA mice. We found that the plasma levels of 20 amine metabolites were significantly decreased in the CIA group.

CONCLUSION

The results suggest that a disordered amine response is linked to RA-associated muscle wasting and energy expenditure.

Dose-response characteristics of Clematis triterpenoid saponins and clematichinenoside AR in rheumatoid arthritis rats by liquid chromatography/mass spectrometry-based serum and urine metabolomics

Clematidis Radix et Rhizoma is a traditional Chinese medicine widely used for treating arthritic disease. Clematis triterpenoid saponins (TS) and clematichinenoside AR (C-AR) have been considered to be responsible for its antiarthritic effects. However, the underling mechanism is still unclear because of their low bioavailability. To address of this issue, metabolomics tools were performed to determine metabolic variations associated with rheumatoid arthritis (RA) and responses to Clematis TS, C-AR and positive drug (Triptolide, TP) treatments. This metabolomics investigation of RA was conducted in collagen-induced arthritis (CIA) rats. Liquid chromatography/mass spectrometry and multivariate statistical tools were used to identify the alteration of serum and urine metabolites associated with RA and responses to drug treatment. As a result, 45 potential metabolites associated with RA were identified. After treatment, a total of 24 biomarkers were regulated to normal like levels. Among these, PC(18:0/20:4), 9,11-octadecadienoic acid, arachidonic acid, 1-methyladenosine, valine, hippuric acid and pantothenic acid etc, were reversed in Clematis TS and C-AR groups. Tetrahydrocortisol was regulated to normal levels in Clematis TS and TP groups, while 3,7,12-trihydroxycholan-24-oic acid was regulated in C-AR and TP groups. Biomarkers like citric acid, p-cresol glucuronide, creatinine, cortolone were reversed in TP group.

Lipid and Metabolic Changes in Rheumatoid Arthritis

While the most obvious manifestations of rheumatoid arthritis (RA) involve inflammation and damage in the synovial joints, the systemic effects of the condition are widespread and life-threatening. Of particular interest is the 'lipid paradox' of RA, where patients with a numerically equivocal starting lipid profile have a significantly raised risk of cardiovascular (CV) events and response to therapy results in a 'normalization' of lipid levels and reduction in events. Changes in lipids can be seen before overt disease manifestations which suggest that they are closely linked to the more widespread inflammation-driven metabolic changes associated with tumour necrosis factor (TNF). Cachexia involves a shift in body mass from muscle to fat, which may or may not directly increase the cardiovascular risk. However, since TNF inhibition is associated with reduction in cardiovascular events, it does suggest that these widespread metabolic changes involving lipids are of importance. Analysis of single lipids or metabolites have been used to identify some of the key changes, but more recently, metabolomic and lipidomic approaches have been applied to identify a broad spectrum of small molecule changes and identify potentially altered metabolic pathways. Further work is needed to understand fully the metabolic changes in lipid profiles and identify novel ways of targeting desired profile changes, but work so far does suggest that a better understanding may allow management of patients to downregulate the systemic effects of their disease that puts them at risk of cardiovascular complications.