PTGS2 and Alzheimer disease: Many diseases that are common in the elderly such as obesity, sarcopenia, insulin resistance, type 2 diabetes mellitus, hypertension, CHD, Alzheimer’s disease, depression, cancer are all associated with a decrease in the activities of desaturases, enhanced activity of COX-2 and altered expression of LOX enzymes and possibly, decreased activity of 15-PGDH, and a frank deficiency or subclinical deficiency of various co-factors needed for adequate metabolism of EFAs such as vitamins B1, B6, B12, folic acid, and various minerals and trace elements could be the underlying cause for excess of PGE2.