BDNF and Alzheimer disease: The third set includes blood neurotrophic biomarkers (e.g., brain-derived neurotrophic factor [BDNF], insulin-like growth factor 1 [IGF-1], and short-chain acylcarnitines [SCACs]) that are found to promote neurogenesis [11, 12] and protect against cognitive decline [13, 14] and incident AD [15, 16].