Increased levels of SAH have been correlated with the severity of outcomes after a high LPS dose (Dai et al., 2016) and are also characteristic of Alzheimer's disease brains, potentially reducing the methyltransferase activity of catechol‐o‐methyltransferase (COMT) and phenylethanolamine N‐methyltransferase (PNMT), enzymes responsible for the catabolism and biosynthesis of catecholamines such as serotonin and dopamine (Kennedy et al., 2004; Ravaglia et al., 2005; Selley, 2007). This evidence concerns the gene PNMT and early-onset autosomal dominant Alzheimer disease.