SUMMARY Caloric restriction, intermittent fasting, time restricted feeding/eating, fasting mimicking diet, and the fuel- switching linked to exercise have all shown evidence of improving metabolic and brain health. Studies funded through the parent grant will be the first to directly address the specific roles of ketone metabolism upon the metabolic, energetic, neuromodulatory, and cognitive benefits conferred by intermittent metabolic switching, which has pleiotropic effects, including augmentation of ketone metabolism. Although focused on neurometabolic declines associated with aging, none of the studies funded through the parent grant directly addresses the role of nutrient oscillations, fuel switching, or ketone metabolism in Alzheimer’s Disease (AD). However, extensive literature shows aberrant energy metabolism occurs in AD, including reduced glucose utilization during neurodegeneration. Mild cognitive impairment/AD also is associated with impaired insulin sensitivity and reduced VO2max compared to controls, factors both linked to mitochondrial function. A logical extension of impaired glucose metabolism is the understudied hypothesis that a ketogenic diet could symptomatically benefit AD subjects. Thus, multiple trials are targeting ketogenic diets to treat cognitive decline in neurodegenerative diseases, and other interventional approaches that provoke intermittent metabolic switching are also of great interest for AD therapy, including intermittent fasting. The central hypothesis of this supplemental application is that integrated ketone metabolism is responsible for the improvement in AD outcomes attributable to intermittent metabolic switching. The single Specific Aim is to use an accepted mouse model of AD to determine if oscillations in ketogenic flux via intermittent fasting not only provide fuel to the brain, but also improve molecular and histopathological outcomes. The rTg4510 (tauP301L bitransgenic) mouse model will be used to study the formation of neurofibrillary tangles associated with Alzheimer's disease. The effects of intermittent fasting, versus ad libitum-fed control, on metabolic and histopathological outcomes will be quantified in mice with hepatic ketogenic sufficiency and compared to those of mice with genetically programmed ketogenic insufficiency. Cutting edge metabolomics and metabolic flux analyses will be used to quantify brain glucose and ketone utilization, and molecular and histopathological approaches will be used to reveal effects on AD pathogenesis. IMPACT: The benefits of ketogenic therapies on health span are commonly presumed to occur through ketone metabolism, but this has never been proven. The experiments proposed for the Supplement will determine if ketone synthesis in liver for utilization in brain plays a mechanistic role in clinically relevant interventions for AD. Moreover, this work will elucidate specific therapeutic targets for individuals who cannot perform this lifestyle intervention but fo...