APOE and Mental deterioration: Mice transgenic for human APOE4 display mitochondrial dysfunction in neurons,41 and both the double and triple transgenic ad mouse models42,43 display marked mitochondrial dysfunction in skeletal muscle.43,44 Our findings of lower skeletal muscle mitochondrial respiration in MCI participants compared to cognitively healthy older adults support a growing body of evidence associating bioenergetic alterations with cognitive decline.