Specificity of a low free serum histidine concentration for rheumatoid arthritis

Cytidine deaminase activity, C reactive protein, histidine, and erythrocyte sedimentation rate as measures of disease activity in psoriatic arthritis

Cytidine deaminase activity, C reactive protein, histidine, and erythrocyte sedimentation rate were measured in 36 subjects with psoriatic arthritis of varying disease duration and severity. Although cytidine deaminase activity may provide an integrated measure of synovial inflammation in rheumatoid arthritis, neutrophil accumulation in psoriatic plaques compromises this measure in psoriatic arthritis. Low histidine concentrations confirm that this amino acid provides a non-specific index of synovial inflammation. In psoriatic arthritis high C reactive protein concentrations seem to be associated with extensive joint destruction. In this study the erythrocyte sedimentation rate was found to be the best laboratory guide to clinical disease activity in psoriatic arthritis.

Free radicals, immunoglobulins and complement as mediators of inflammation

There is evidence for both oxygen-centred free radicals and products of complement activation acting as mediators of inflammation. Evidence for the generation and reaction of free radicals at sites of inflammation can only be indirect and circumstantial due to their very transient nature. Evidence for complement activation in several inflammatory conditions, including rheumatoid arthritis is strong. These mediator classes individually possess a range of potential proinflammatory activities. Their effects may be linked through the formation of immune complexes and the activation of polymorphonuclear leukocytes. Their actions will also be linked with and modulated by the activities of other mediators mentioned only briefly in this chapter. The relative importance of the different mediators in any particular inflammatory condition is difficult to ascertain. The importance of free radicals and complement will be better understood when drugs specifically and unequivocally aimed at their control are identified. This potential for therapeutic advances in the treatment of inflammatory disorders has yet to be realized.

Kinetic investigations into the possible cause of low serum histidine in rheumatoid arthritis

To investigate the cause of low serum histidine in rheumatoid arthritis (RA) single oral and intravenous doses of L-histidine were administered to patients with active RA, and to an equal number of age and sex matched control subjects. In the first study 13 patients and their controls received a 100 mg kg-1 dose of L-histidine as an aqueous slurry. Significant differences were seen in body weight, predose baseline serum histidine concentration, Cmax, t1/2, and area under curve, AUC0-infinity. In a second study six patients and six controls each received a 50 mg kg-1 dose of L-histidine both orally and intravenously on two separate occasions. The patients with RA had a lower baseline serum histidine concentration, a lower volume of distribution, and a shorter plasma half life than the controls, but these differences were not statistically significant. No difference was seen in bioavailability or clearance. Low serum histidine in RA is unlikely to be due to malabsorption from the gut, uptake by abnormal gut flora, or increased metabolism.

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.

The effect of drugs on serum histidine levels in rheumatoid arthritis

Groups of 15 patients with active rheumatoid arthritis were treated for 24 weeks with zinc sulphate, trien, captopril, clozic in two doses or a combination of D-penicillamine and hydroxychloroquine. Serum histidine levels were monitored along with measures of disease activity including C-reactive protein, plasma viscosity, articular index, grip strength and early morning stiffness. Zinc sulphate and trien were found to be ineffective while the other drugs all showed evidence of second-line action. Serum histidine was found to improve during successful therapy. The possible cause of low serum histidine and its response to therapy is discussed.

Serum histidine in rheumatoid arthritis: a family study

We have compared free serum histidine in patients with rheumatoid arthritis, their blood relatives, and their non-blood relatives. The hypohistidinaemia of rheumatoid arthritis is acquired with the disease and does not provide a biochemical marker of those at risk.

A comparison of serum biochemistry in ankylosing spondylitis, seronegative and seropositive rheumatoid arthritis

The serum biochemistry of 31 patients with ankylosing spondylitis (AS) was compared with that of 80 patients with rheumatoid arthritis (RA) (ARA criteria), 30 of whom were negative for circulating rheumatoid factor and 50 of whom were 'seropositive'. All patients were selected because of moderate to severe disease activity. All 3 groups had distinctive biochemical profiles. Total serum sulphydryl and haemoglobin were particularly good discriminators between AS and RA, IgG, IgA, and acute-phase reactants complemented the sheep cell agglutination test in discriminating between seropositive RA and seronegative RA. In active AS a normal erythrocyte sedimentation rate was often seen in the presence of abnormal C-reactive protein (CRP) and plasma viscosity.

Discriminatory indices of response of patients with rheumatoid arthritis treated with D-penicillamine

A long-term study is being undertaken to classify drugs used as specific agents in the treatment of rheumatoid arthritis in terms of their effects on biochemical and clinical characteristics of the disease. In particular is hoped to establish those indices which are most relevant to the response of RA to treatment. Fifteen patients were treated with D-penicillamine after an initial period of 2 weeks on aspirin alone, when the baseline investigations were made. The dose of penicillamine was increased gradually to a maximum of 500 mg a day over the period of 6 months, and changes in 8 clinical and 25 laboratory indices were measured on 8 separate occasions in the 6-month period. Marked clinical improvement took place, and this was mirrored by changes in a wide range of biochemical parametaers. ESR and C-reactive protein were shown to be the most suitable indices of disease improvement with penicillamine treatment.