Level of glial cell derived neurotrophic factor in the blood plasma of rheumatoid arthritis patients and its relationship with alexithymia.

Introduction: Glial cell derived neurotrophic factor (GDNF) has an important role in the pathogenetic mechanisms and clinical manifestations of rheumatoid arthritis (RA). Alexithymia is associated with a severe clinical course and worse prognosis, while the relationship between alexithymia and GDNF in RA patients has not been investigated before. The aims of the study were to investigate the GDNF level in blood plasma in RA patients depending on the presence of alexithymia and to evaluate the relationship of GDNF level with clinical manifestation and quality of life.

Material and methods: Fifteen men and 73 women with RA were examined using the Disease Activity Score with 28-joint count (DAS28) with erythrocyte sedimentation rate (ESR) index, the Simple Disease Activity Index (SDAI), the Rheumatoid Arthritis Clinical Disease Activity Index (CDAI), the Visual Analogue Scale (according to the assessment of the patient - VAS-P and the assessment of the doctor - VAS-D), the Health Assessment Questionnaire (HAQ), the Toronto Alexithymia Scale (TAS-20), the Disability Rating Index (DRI) and SF-36 indexes. Glial cell derived neurotrophic factor level in the blood plasma was determined by enzyme-linked immunosorbent assay (ELISA).

Results: Forty percent of RA patients had alexithymia. Glial cell derived neurotrophic factor level in the examined patients was 3.73 ±2.59 pg/ml, in patients with alexithymia 4.08 ±2.87 pg/ml, without alexithymia 3.48 ±2.37 pg/ml (p = 0.295). Patients with alexithymia had a higher erythrocyte sedimentation rate (ESR) and index scores than patients without alexithymia - ESR: 34.29 ±14.22 vs. 22.73 ±12.03 mm/h (p = 0.017), DAS28: 6.53 ±0.66 vs. 6.09 ±0.55 (p = 0.017), VAS-D: 7.19 ±0.81 vs. 6.53 ±0.83 (p = 0.020), HAQ: 1.78 ±0.58 vs. 1.51 ±0.54 (p = 0.040). Also they had worse SF-36 indicators - physical functioning: 39.52 ±13.78 vs. 51.00 ±14.90 (p = 0.019), role functioning due to physical condition: 30.95 ±20.77 vs. 46.67 ±24.76 (p = 0.041), physical component of health: 31.47 ±11.44 vs. 41.61 ±15.88 (p = 0.028). In patients with alexithymia, a correlation was found between the GDNF level and severity of pain according to VAS-P: r_S = 0.338, p = 0.044, and VAS-D: r_S = 0.446, p = 0.006.

Conclusions: Alexithymia was found in 40% of RA patients. Rheumatoid arthritis patients with alexithymia had a nonsignificantly higher GDNF level compared to patients without alexithymia. In RA patients with alexithymia, an association of GDNF level in the blood plasma with RA activity, loss of functional capacity and reduced quality of life was established. Alexithymia in RA patients is an important factor in the clinical manifestation of RA and modification of the pathophysiological role of GDNF.