Plasma levels of Aβ42 were increased in DIO mice in comparison with age-matched RC-fed controls, to levels that were not significantly different from that obtained in RC-fed AD transgenic mice expressing human APP with the Swedish mutation (hAPPSw mice), with BACE1-KO mice displaying very low plasma Aβ42 levels (Figure 1G; diet × genotype, P < 0.01). Here, BACE1 is linked to Alzheimer disease.