Glutamate modulates bone destruction of the TMJ in rheumatoid arthritis

Objectives: The aim of this study was to investigate the relation between plasma level of glutamate and extent of radiographic bone erosion of the TMJ in patients with early RA in relation to sex-steroid hormones.

Methods: 47 patients (29 women and 18 men) of whom 24 (51%) were seropositive were included within 23 days after being diagnosed with RA. Radiographic signs of bone erosion in the TMJ was recorded by cone-beam CT images and a score (0 - 24) was calculated for each patient. Venous blood was analyzed for C-reactive protein, glutamate and the sex hormones estrogen, progesterone and testosterone. Nonparametric and parametric statistical methods were used in the analysis when applicable.

Results: There was a significant positive correlation between plasma level of glutamate and extension of radiographic erosions that was stronger in the female patients with estradiol level < 50 pmol/L. No other relation was found between glutamate and the sex steroid hormones in determining bone erosion. The erosions did not correlate with degree of systemic inflammation as expressed by C-reactive protein or rheumatoid factor.

Conclusion: This study shows that systemic glutamate is associated with the extent of radiographic erosions of the TMJ. The relationship between glutamate and erosions seems to be reinforced by low estradiol level. Supported by National Institute of Dental and Craniofacial Research Grant 1 R01 DE15420-01