Association of serum BDNF and val66met polymorphism of the brain-derived neurotrophic factor in a sample of first psychotic episode patients.

Polymorphisms in the brain-derived neurotrophic factor (BDNF) gene have been indicated to be associated with schizophrenia. Previous studies have suggested that val66met polymorphism may increase the risk for schizophrenia, although other studies have not confirmed this association. Decreased BDNF levels in the brain and the serum of patients with psychotic disorders have been reported in first episode psychotic (FEP) patients. In our study we investigated the potential genetic association of this polymorphism with schizophrenia in a sample of 38 FEP patients with schizophrenia compared with a sample of 21 normal controls. Furthermore, we assessed serum BDNF levels and investigated whether there was an association between this polymorphism and alterations of serum BDNF levels between the investigated groups. There was a significant difference in genotyped frequencies between cases and controls (p=0.030). The homozygous carriers Met/Met were over-represented in the schizophrenia group (13/31, 41.9%), compared to controls (2/19, 10.5%). The serum BDNF levels in the sample of FEP patients was significantly reduced compared to controls (18.87±8.23 ng/mL vs 29.2±7.73ng/mL, U=140, p=0.0). No association was found between alterations of serum BDNF levels and Val66Met polymorphism in the group of patients (p=0.198). Negative correlations were shown between serum BDNF levels of the patients and the PANSS Negative subscale scores (p=0.015). There was found no significant difference between genotypes and memory scores in the sample of patients. Our findings indicate that serum BDNF levels at the onset of schizophrenia and BDNF Val66Met variant may be susceptibility risk factors for schizophrenia.