Endogenous Glutamate in Association With Inflammatory and Hormonal Factors Modulates Bone Tissue Resorption of the Temporomandibular Joint in Patients With Early Rheumatoid Arthritis

Purpose The aim of this study was to investigate the relation between plasma level of glutamate and extent of radiographic bone erosion of the temporomandibular joint (TMJ) in patients with early rheumatoid arthritis (RA) in relation to inflammatory disease activity as well as estradiol and testosterone. Materials and Methods A total of 47 patients (29 women and 18 men) of whom 24 were seropositive were included shortly after being diagnosed with RA. Radiographic signs of bone tissue resorption (erosions) in the TMJ were recorded by cone-beam CT images, and an erosion score (0 to 24) was calculated for each patient. Venous blood was analyzed for rheumatoid factor, C-reactive protein, erythrocyte sedimentation rate, leukocyte particle count, glutamate, estradiol, and testosterone. Nonparametric statistical methods were used in the analysis. Results Resorptive changes of the TMJ were found in a major part of the patients. There was a significant positive correlation between plasma level of glutamate and extension of radiographic erosions that was strongest in the patients with low levels of C-reactive protein, estradiol, or testosterone. By contrast, erosions were correlated with C-reactive protein in patients with high levels of estradiol. The highest levels of glutamate were found in patients with low levels of C-reactive protein and estradiol. Conclusions This study shows that a majority of patients with early RA presents radiographic signs of bone tissue resorption of the TMJ and that circulating glutamate is associated with the extent of these changes. The relationship between glutamate and bone resorption seems to be influenced by systemic inflammatory activity as well as estradiol and testosterone levels.