Sirt 1 gene expression and its regulation early in life is central to hepatic glucose, cholesterol, and amyloid beta metabolism and their downregulation in stages 1–3 of AD (Figure 2) avoid errors with relevance to proteomic (adiponectin, FGF21) and lipidomic (ceramides, sphingolipids) analysis that may show increased or altered levels in plasma and CSF in later stages 4–7 of AD. Here, FGF21 is linked to Alzheimer disease.