Brain-derived neurotrophic factor-TrkB signaling and the mechanism of antidepressant activity by ketamine in mood disorders

Excerpt

Brain-derived neurotrophic factor (BDNF) plays a key role in the pathophysiology of mood disorders such as major depressive disorder (MDD) and bipolar disorder (BD). According to the Biomarkers Definitions Working Group, BDNF is one of the most frequently investigated blood biomarkers in mood disorders. In this issue, Schröter et al. [1] investigated longitudinal multi-level biomarker analysis of BDNF in patients with MDD (n = 49), BD (n = 37) and healthy control subjects (n = 57). The serum level of BDNF in patients with MDD was significantly lower than that in the healthy controls, but there was no difference between the serum levels of BDNF in the BD patients and healthy controls. Furthermore, methylation of BDNF exon I promoter in patients with MDD, but not BD patients, was significantly higher than that of healthy controls. However, there were no differences in serum BDNF levels and BDNF methylation between the samples from admission and discharge from the hospital. Furthermore, Engelmann et al. [2] reported that patients with MDD (n = 39) who exhibited a normalization of memory dysfunction (i.e., delayed recall performance) had significantly higher plasma BDNF levels from baseline to day 56 than patients with persistent deficits (n = 43), suggesting that BDNF influences the mechanisms underlying the normalization of memory dysfunction in MDD. However, the ELISA kit used in this study can recognize both BDNF (mature form) and its precursor proBDNF [3]. Given the opposite roles of BDNF (mature form) and proBDNF, further studies using ELISA kits that can specifically differentiate into mature BDNF and proBDNF are needed. …