TREM2 and Alzheimer disease: Exercise training can effectively reduce the prevalence of AD and alleviate its symptoms through the modulation of multiple signaling pathways involved in the pathophysiological process of AD, including the PI3K/Akt, Wnt/β-catenin, AMPK-related, MAPK, NF-κB, PINK1-PARKIN, JAK/STAT, and TREM2 signaling pathways.