Using transgenic and somatic gene transfer approaches to achieve a continuous supply of kallikrein–kinin in vivo, the tissue kallikrein–kinin system (KKS) exhibits protective effects in hypertension, associated insulin resistance in type 2 diabetes, cardiovascular, renal and central nervous systems via suppression of oxidative stress [13], [14]. Here, KLK4 is linked to type 2 diabetes mellitus.