[Cognitive function, serum BDNF levels and BDNF gene Val66Met polymorphism in amnestic mild cognitive impairment]

To investigate the relationship between serum brain-derived neurotrophic factor, concentrations and BDNF gene Val66Met polymorphism and amnestic mild cognitive impairment (aMCI), and neuropsychological characteristics.

Ninety-nine aMCI patients and 99 matched normal controls were recruited for the study. Multi-dimension neuropsychologic tests were used to extensively assess the cognitive function, an enzyme-linked immunosorbent assay was applied to measure serum BDNF concentrations, and polymerase chain reaction-restriction fragment length polymorphism was used to analyse BDNF gene Val66Met polymorphism in the subjects.

The scores of neuropsychologic tests in aMCI patients were significantly lower than those in the normal controls (all P<0.001), with the largest impairment on delayed recall of the auditory verbal memory test (AVMT) which reflect verbal episodic memory. The serum concentrations of BDNF in aMCI patients (median: 4.37 microg/L) were significantly lower than those of the normal controls (median: 4.98 microg/L) (z=-2.449, P=0.014). There was positive correlation between the serum concentrations of BDNF and the scores on delayed recall of AVMT (r=0.264, P=0.008). No significant differences were found for the genotype and allele distribution of BDNF Val66Met polymorphism between aMCI patients and the normal controls. BDNF Val66Met polymorphism was not associated with serum BDNF concentrations and cognitive assessment scores in aMCI patients (P>0.05).

aMCI is characterized by episodic memory impairment. Decreased BDNF concentrations may play a role in the pathophysiology of aMCI, and BDNF gene Val66Met polymorphism may not be an important genetic factor in susceptibility to aMCI.