New research reveals how a protein linked to Alzheimer’s risk can alter the way the brain’s immune cells process fat and trigger inflammatory responses, offering a possible explanation for how the strongest genetic risk factor for the disease affects the brain.

APOE4, the strongest genetic risk factor for Alzheimer's disease, changes how microglia process fat, according to laboratory work with human microglia published in Alzheimer's & Dementia. Cells carrying ApoE4 formed fewer but larger lipid droplets and had fewer mitochondria, and lipid-free ApoE4 triggered stronger inflammatory responses. The findings offer a possible mechanistic explanation for how APOE4 raises Alzheimer's risk.