Serum BDNF and GDNF in Chinese male patients with deficit schizophrenia and their relationships with neurocognitive dysfunction

BACKGROUND: To measure the serum levels of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) in deficit schizophrenia (DS), in order to examine the association between these two neurotrophic factors (NFs) and cognitive performance. METHODS: A total of 109 male patients [51 DS and 58 non-deficit schizophrenia (NDS)] with schizophrenia and 40 sex and age matched healthy controls (HC) participated in this study. Processing speed, attention, executive function, and working memory of all subjects were assessed by means of a battery of classical neuropsychological tests. Serum BDNF and GDNF levels were measured simultaneously using a double-antibody sandwich enzyme-linked immunosorbent assay (ELISA). RESULTS: There were significant differences in the overall cognitive test scores between three groups (all p < 0.001). Serum BDNF levels were significantly lower in patients (DS and NDS) than in HC (p < 0.001). Furthermore, BDNF levels were lower in the DS compared to the NDS group, although not significantly. However, there was no difference in the GDNF levels between patients (DS and NDS) and HC. GDNF levels were positively correlated with scores of Stroop words only (r = 0.311, p = 0.033), Stroop colors only (r = 0.356, p = 0.014) and Stroop interference (r = 0.348, p = 0.016) in DS group. CONCLUSION: Serum BDNF may be an unsuitable biomarker for DS, despite a significant decrease in schizophrenia patients. The different neurocognitive performance between the DS and NDS patients indicates that DS may be a separate clinical entity of schizophrenia. Finally, higher serum GDNF levels are associated with better cognitive performance in DS patients, indicating a possible neuroprotective function in DS.