APP and Alzheimer disease: To test whether systemic leptin alters hippocampal microglia in AD, male APP/PS1 adult (6 months) and aged (12 months) mice received daily intraperitoneal leptin (1 mg/kg) or vehicle for 7 days, followed by quantification of brain Aβ burden and hippocampal microglial activation (Iba-1+ cells) and cytokines (IL-1β, IL-6).