HACD3 and Alzheimer disease: Based on previous studies, these proteins have been involved in OXPHO as well as in Huntington disease, Alzheimer disease, Parkinson disease, retrograde endocannabinoid signaling, and nonalcoholic fatty liver disease (NAFLD) (Fig 3B, S3D Fig and S3 Data), whereas a group of proteins including acetyl-CoA acyltransferase 2 (ACAA2), aldehyde dehydrogenase 2 (ALDH2), hydroxyacyl-CoA dehydrogenase (HADH), carnitine palmitoyltransferase 2 (CPT2), and 3-hydroxyacyl-CoA dehydratase 3 (HACD3) were highly expressed in iTreg cells and were clustered as a module named fatty acid metabolism.