Relative to controls, individuals with preclinical AD showed lower levels of neurosecretory protein VGF (VGF), neuronal pentraxin-2 (NPTX2), brain-derived neurotrophic factor (BDNF) and cadherin-2 (CDH2) and higher levels of FXYD domain containing ion transport regulator 6 (FXYD6). Here, BDNF is linked to Alzheimer disease.