CSF: cerebral spinal fluid; INI: intranasal insulin; AD: Alzheimer’s disease; CT: control subjects; FAAH: fatty acid amide hydrolase; eCB: endocannabinoid system; MCI: mild cognitive impairment; ML: machine learning; CSF: cerebral spinal fluid; sTREM2: soluble trigger receptor expressed on myeloid cells 2; IL: interleukin; MetS: metabolic syndrome; PBMC: peripheral blood mononuclear cell. The gene discussed is FAAH; the disease is metabolic syndrome.