PSEN1 and Alzheimer disease: Exenatide reduces Aß42 levels [10] and amyloid plaque area in the hippocampus [11] in AD transgenic models, and similarly exendin-4 decreases amyloid plaque load and soluble Aß levels in the cortex and hippocampus in APP/PS1 mice and Aß1-42 injected rats [12, 13].