AMINO-ACID CONTENT OF SERUM IN RHEUMATOID ARTHRITIS

Exhaled nitric oxide in early rheumatoid arthritis and effects of methotrexate treatment

Patients with established rheumatoid arthritis (RA) and disease modifying treatments have lower nitric oxide (NO) levels in the alveolar compartment (C_ANO) and in the airway wall (C_awNO), but also higher diffusion capacities for NO in the airways (D_awNO) compared to matched controls. The aim of the present study was to investigate the NO lung dynamics in patients with recent onset RA before and after immune suppression with methotrexate therapy. Patients with early RA and antibodies against anticitrullinated peptides (ACPA) were recruited. Measurement of exhaled NO and inflammatory markers in serum were performed. Clinical disease activity was evaluated with Disease Activity Score for 28 joints. Healthy individuals were used as matched controls. Data are presented as median (lower quartile, upper quartile) values. RA patients (n = 44) had lower exhaled NO (F_ENO₅₀) 16 (10–24) ppb compared to controls 21 (15, 29) ppb, p = 0.013. In NO-dynamics, C_ANO was lower in RA patients 1.6 (1.0, 2.2) ppb compared to the control subjects 2.3 (1.3, 3.1) ppb, p = 0.007. C_awNO was also lower in the RA patients 55 (24, 106) ppb compared to control subjects 124 (110, 170) ppb, p < 0.001, but D_awNO was higher 17 (8, 30) mL/s and 9 (5, 11) mL/s respectively, p < 0.001. Methotrexate treatment for three months reduced disease activity, but did not change the NO dynamics. In conclusion, the altered NO dynamics of the lung in ACPA-positive RA patients are already present in the early stages of the disease before any treatments and do not change after methotrexate therapy suggesting a role in the pathogenesis.

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).

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.

Plasma concentrations of amino acid and nicotinamide metabolites in rheumatoid arthritis--potential biomarkers of disease activity and drug treatment

This study aimed to evaluate changes in plasma amino acid and nicotinamide metabolites concentrations in rheumatoid arthritis (RA) in a search for potential biomarkers of the disease activity and the effect treatment. Analysis of plasma metabolite patterns with liquid chromatography/mass spectrometry revealed specific changes in RA as well as correlations with clinical parameters. Combined concentration parameter calculated as [aspartic acid] + [threonine] + [tryptophan] - [histidine] - [phenylalanine] offered the strongest correlation (p < 0.001) with pain joint count, swollen joint count and DAS 28. Such analysis of amino acid and related metabolite pattern offers potential for diagnosis as well as for monitoring disease progression and therapy in RA.

Colorimetric visualization of glucose at the submicromole level in serum by a homogenous silver nanoprism-glucose oxidase system

In this study, we design a homogeneous system consisting of Ag nanoprisms and glucose oxidase (GOx) for simple, sensitive, and low-cost colorimetric sensing of glucose in serum. The unmodified Ag nanoprisms and GOx are first mixed with each other. Glucose is then added in the homogeneous mixture. Finally, the nanoplates are etched from triangle to round by H2O2 produced by the enzymatic oxidation, which leads to a more than 120 nm blue shift of the surface plasmon resonance (SPR) absorption band of the Ag nanoplates. This large wavelength shift can be used not only for visual detection (from blue to mauve) of glucose by naked eyes but for reliable and convenient glucose quantification in the range from 2.0 × 10(-7) to 1.0 × 10(-4) M. The detection limit is as low as 2.0 × 10(-7) M, because the used Ag nanoprisms possess (1) highly reactive edges/tips and (2) strongly tip sharpness and aspect ratio dependent SPR absorption. Owing to ultrahigh sensitivity, only 10-20 μL of serum is enough for a one-time determination. The proposed glucose sensor has great potential in the applications of point-of-care diagnostics, especially for third-world countries where high-tech diagnostics aids are inaccessible to the bulk of the population.

Plasma amino acids in rheumatoid arthritis

Plasma amino acid concentrations have been investigated in 12 female patients with rheumatoid arthritis (RA), who were hospitalized for two 14-day periods, one of which included 7 days of total fasting, whereas the other served as control period with normal food intake. All medical treatment was stopped on admission to the hospital. Plasma amino acid levels were repeatedly determined during both periods. Another group, consisting of 8 healthy volunteers, also underwent total fasting, for 6 days. The response to food deprivation with regard to plasma amino acid levels was compared with that in the RA patients. The results obtained from the control period were compared with those derived from age and sex matched healthy controls. RA disease was not characterized by a typical amino acid pattern. Major increases were seen in the concentrations of taurine, aspartate, glutamate, glycine, 1-methyl histidine, isoleucine and arginine. Rather smaller yet significant elevations could be observed in the levels of cystein, threonine, serine, citrulline, methionine and leucine. The only amino acid to show a lowered concentration was alpha-aminobutyrate. Most of the alterations induced by fasting were similar to those in healthy volunteers. An exception was the levels of taurine, which evidenced in RA patients a further increase during starvation, not observed in healthy volunteers, and valine which exhibited, a smaller increment than that apparent in healthy controls. The increase in sulphur-containing amino acids might be interpreted as a sign of an enhanced glutathione (GSH) catabolism, whereas the differing metabolic behaviour of branched chain amino acids (BCAA) suggests a specific reaction of valine in RA disease, similar to that in other catabolic diseases.

Modification of prostaglandin generation by L-histidine--possible pathogenetic implication in rheumatoid arthritis

The effect of l-histidine on arachidonic acid metabolism was studied in rabbit splenic fibroblast cultures and human platelets. The noradrenaline-stimulated generation of PGE2 in fibroblast cultures was inhibited by l-histidine dose dependently. In the same way l-histidine diminished the aggregation-induced synthesis of TXB2 in human platelets. In contrast to this, after incubation with l-histidine the generation of PGE2 in activated platelets increased in a dose dependent way up to 240% of pretreatment values. The further increase of l-histidine concentration resulted in an inhibition of platelet PGE2 synthesis. The present results demonstrate a differential influence of the amino acid l-histidine on cell arachidonic acid metabolism. It is concluded that the supposed anti-rheumatic property of l-histidine is caused by its effect on the synthesis of prostaglandins which are known to be mediators of inflammation.

Free serum histidine levels in patients with rheumatoid arthritis and control subjects following an oral load of free L-histidine

A dose of 3.7 g of free-L-histidine was administered by mouth to 26 patients with active rheumatoid arthritis and to 29 control subjects. The patients with rheumatoid arthritis had a statistically significant (p=10(-12)) lower pretreatment concentration of free histidine in serum (1.20 mg/100 ml, SE=0.04) than the control subjects (1.90 mg/100 ml, SE=0.06). However, there were no statistically significant differences between rheumatoid and control subjects with respect to the serum histidine concentrations 1 hr, 3 hr, and 4 hr after the ingestion of L-histidine. The changes in the serum histidine concentrations at 1 hr, 3 hr, and 4 hr (compared to the pretest values) were also not significantly different in the patients with rheumatoid arthritis relative to the control subjects. This study suggests that the subnormal free serum histidine concentration of rheumatoid arthritis is not associated with abnormal serum levels of free histidine following an oral load of free histidine.

Inhibition of denaturation of human gamma globulin by a mixture of L-histidine, L-cystine, and copper, and its clinical implication in rheumatoid arthritis

A mixture of histidine, cystine, and copper mimicked gold thiomalate, N-ethylmaleimide, and p-chloro-mercuribenzoic acid in inhibiting sulfhydryl-disulfide interchange-mediated denaturation of human gamma globulin, bovine serum albumin, and diluted human serum. Measurable inhibitory effects were obtained with a mixture of physiologic concentrations of L-histidine, L-cystine, and copper. This work suggests a mechanism by which the hypohistidinemia of rheumatoid arthritis could contribute to the pathogenesis of the disease.

Hypohistidinemia in juvenile rheumatoid arthritis

The mean level of plasma histidine in 86 children with rheumatoid arthritis was found to be significantly lower in comparison with that of controls. The possible influence of various drugs on the plasma histidine concentration is discussed.

Low free serum histidine concentration in rheumatoid arthritis. A measure of disease activity

A study of sera from 285 patients with definite or classical rheumatoid arthritis (including 37 patients receiving no anti-inflammatory drugs) and sera from 67 healthy subjects has confirmed 10 published reports of a statistically significant decreased blood histidine concentration in patients with rheumatoid arthritis. Contrastingly, in sera from 231 patients with a variety of acute and chronic illnesses other than rheumatoid arthritis, no statistically significant hypohistidinemia was observed either in the group as a whole or in association with the administration of aspirin, prednisone, indomethacin, phenylbutazone, or dextropropoxyphene. In the patients with rheumatoid arthritis there was a statistically significant correlation between the serum histidine concentration and the following: Westergren sedimentation rate (r=-0.33, P smaller than 10- minus 9), grip strength (r=0.26, P smaller than 10- minus 9), hematocrit (r=0.23, P smaller than 10- minus 9), duration of morning stiffness (r=-0.14, P=10- minus 5), walking time (r=-0.13, P=10- minus 4), latex titer of rheumatoid factor (r=-0.11, P=0.001), and the duration of arthritis (r=-0.06, P=0.05). There was no statistically significant association between the serum histidine concentration and the duration of rheumatoid arthritis in the 151 patients with disease of 0-10-yr duration (r=0.02, P=0.5), the sex of the patient, or the presence of antinuclear antibody (R=0.007, P=0.9). The serum histidine concentration was less in rheumatoid patients receiving steroids (P=0.00001), gold (P=0.009), and aspirin (P=0.15) than in rheumatoid patients not receiving these drugs. This study indicates that histidine determinations on properly preserved casual serum samples can be helpful in the diagnosis of rheumatoid arthritis and in the evaluation of the activity of the disease.