BDNF Val66Met moderates memory impairment, hippocampal function and tau in preclinical autosomal dominant Alzheimer's disease

Abstract

SEE ROGAEVA AND SCHMITT-ULMS DOI101093/AWW201 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: The brain-derived neurotrophic factor (BDNF) Val66Met polymorphism is implicated in synaptic excitation and neuronal integrity, and has previously been shown to moderate amyloid-β-related memory decline and hippocampal atrophy in preclinical sporadic Alzheimer's disease. However, the effect of BDNF in autosomal dominant Alzheimer's disease is unknown. We aimed to determine the effect of BDNF Val66Met on cognitive function, hippocampal function, tau and amyloid-β in preclinical autosomal dominant Alzheimer's disease. We explored effects of apolipoprotein E (APOE) ε4 on these relationships. The Dominantly Inherited Alzheimer Network conducted clinical, neuropsychological, genetic, biomarker and neuroimaging measures at baseline in 131 mutation non-carriers and 143 preclinical autosomal dominant Alzheimer's disease mutation carriers on average 12 years before clinical symptom onset. BDNF genotype data were obtained for mutation carriers (95 Val₆₆ homozygotes, 48 Met₆₆ carriers). Among preclinical mutation carriers, Met₆₆ carriers had worse memory performance, lower hippocampal glucose metabolism and increased levels of cerebrospinal fluid tau and phosphorylated tau (p-tau) than Val₆₆ homozygotes. Cortical amyloid-β and cerebrospinal fluid amyloid-β₄₂ levels were significantly different from non-carriers but did not differ between preclinical mutation carrier Val₆₆ homozygotes and Met₆₆ carriers. There was an effect of APOE on amyloid-β levels, but not cognitive function, glucose metabolism or tau. As in sporadic Alzheimer's disease, the deleterious effects of amyloid-β on memory, hippocampal function, and tau in preclinical autosomal dominant Alzheimer's disease mutation carriers are greater in Met₆₆ carriers. To date, this is the only genetic factor found to moderate downstream effects of amyloid-β in autosomal dominant Alzheimer's disease.

Keywords: Alzheimer’s disease; amyloid-β; dementia; genetics; tau.