Glial cell line-derived neurotrophic factor (GDNF) in blood serum and lacrimal fluid of patients with a current depressive episode

Background: Many studies indicate a significant role of GDNF in the pathogenesis of the mood disorders, including bipolar disorder (BD) and major depressive disorder (MDD). Potentially, neurotrophic factors in lacrimal fluid (LF) could become biomarkers of various specific disorders. The aim of this study was to assess GDNF levels in LF and blood serum (BS) of patients with a current depressive episode (cDE). Methods: We studied the glial cell line-derived neurotrophic factor (GDNF) concentration in the LF and BS of 39 healthy controls and 137 patients with a current depressive episode (cDE) (both subgroups members were 20-49 years): BD - 46 patients, MDD - 91 patients. Results: GDNF concentration in BS of women with MDD was significantly lower than in men. In BD patients, univariate linear regression analysis revealed significant correlations between GDNF concentration in the LF and the use of anxiolytics or antidepressants. These correlations were confirmed by the multivariate linear regression analysis. A significant correlation between GDNF concentrations in the LF and BS was found in controls. Limitations: The unequal proportion of men in the BD group did not permit adjusting GDNF concentrations for sex. The collected LF was stimulated, which could influence GDNF levels. It should also be noted that the patients included in the study were not treatment- naive. Conclusions: Our findings suggest that GDNF concentration in LF could be a biomarker of the cDE (both unipolar and bipolar), though the sensitivity of this potential biomarker may be lower in depressive patients with anxiety symptoms.

Automated summary

This study aimed to evaluate the concentration of GDNF in tears and serum of patients with a current depressive episode. The results showed that GDNF concentration in the serum was significantly lower in women with MDD, and in BD patients, there was a significant correlation between GDNF concentration in tears and the use of anxiolytics or antidepressants. A significant correlation between GDNF concentrations in tears and serum was found in the control group. In conclusion, GDNF concentration in tears could be a biomarker of the current depressive episode.