Brain-derived neurotrophic factor (BDNF) can promote neuronal growth and repair, playing a key role in synaptic plasticity, especially in the hippocampus. The BDNF Val66Met polymorphism was shown to strongly affect BDNF function, but its role in modulating gray matter damage in multiple sclerosis (MS) patients is still not clear.
Considering BDNF relevance on hippocampal function, we aimed to explore the effect of BDNF Val66Met polymorphism on the atrophy of hippocampal subfields and its role in cognitive functioning in MS patients.
Using a 3T scanner, we obtained dual-echo and 3DT1-weighted sequences from 50 MS patients and 15 healthy controls (HC). MS patients also underwent genotype analysis of BDNF and an extensive neuropsychological evaluation. Hippocampal subfields were segmented by using Freesurfer 7.0.1 software. Multiple linear regression models adjusted for age, sex and disease duration were used for between-group comparisons and analysis of associations.
The BDNF Val66Met polymorphism was found in 22 MS patients (44%). Compared to HC, MS patients had reduced volumes of: bilateral hippocampus-amygdala transition area (HATA); left cornus ammonis (CA)1, CA3 and granule cell layer of dentate gyrus (GCL-DG); and right fimbria and presubiculum. BDNF Val66Met polymorphism carriers compared to wild-type (Val66Val) MS patients had higher volume of left hippocampal CA1, CA3, CA4, GCL-DG, molecular layer of subiculum and HATA; and of right hippocampal tail, fissure and presubiculum. In MS patients, higher volume in left CA3 and in right presubiculum correlated with better performance in semantic fluency, while higher volume in left GCL-DG correlated with better visuo-spatial memory performance.
The BNDF Val66Met polymorphism has a protective role in MS patients against both hippocampal atrophy and cognitive deterioration. BDNF genotype may be a potential biomarker for predicting cognitive prognosis, and an interesting target to study for neuroprotective strategies.