As multiple studies now show an impact of APOE on brain bioenergetics, which occurs prior to the onset of significant AD pathologies (Reiman et al., 1996), it is anticipated that improving our understanding of the L-carnitine system will help us better appreciate these early bioenergetics changes that could precede brain amyloid and tau pathologies and as such provide avenues for AD prevention. The gene discussed is MAPT; the disease is Alzheimer disease.