INS and Insulin resistance: Specifically, BACE1 expression levels inversely correlate with body weight, lipid and glucose homeostasis [31]; PSEN1 directly downregulates the expression of insulin receptor [28]; neprilysin upregulation is correlated with insulin resistance [56] while its decrease is associated with enhanced insulin sensitivity [61, 64]; IDE directly degrades insulin [34, 35] and is upregulated in brain cells with aberrant cell cycle activity [59].