PPARD and Alzheimer disease: LXR is a member of a group of nuclear receptors, peroxisome proliferator-activated receptors (PPARs; other members are PPARγ and PPARδ), each of which upon activation heterodimerizes with retinoid X receptor (RXR) to form a functional transcription factor along with coactivators that act to regulate expression of many genes, including those involved in AD pathogenesis [34].