Serum protein levels of brain-derived neurotrophic factor and tropomyosin-related kinase B in bipolar disorder: Effects of mood stabilizers

Aim:In this study, we investigated serum protein levels of brain-derived neurotrophic factor (BDNF) and its receptor tropomyosin-related kinase B (TrkB) in patients with bipolar disorder. Methods:Over a 2-year period, 26 patients with bipolar I disorder (manic episode) and 56 healthy controls were recruited. The Young Mania Rating Scale scores of patients with bipolar mania were >26. Serum BDNF and TrkB protein levels were measured with ELISA kits. Results: Using ANCOVA with age adjustment, we found that there were no significant differences in serum BDNF protein levels between patients with bipolar mania and healthy controls (p = 0.582). In contrast, the serum TrkB protein level was significantly higher in bipolar mania patients than in healthy controls (p = 0.001), especially in women (p = 0.001). Of 26 patients with bipolar mania, 21 underwent a second measurement of serum BDNF and TrkB protein levels after a 4-week treatment with mood stabilizers. There were no significant changes in serum BDNF or TrkB protein levels. Conclusion:These findings suggest that serum TrkB protein levels may play an important role in the psychopathology of bipolar mania. However, a larger sample size is needed to confirm these results.