It has been reported that resistin concentration in human healthy subjects’ saliva ranges between 4.4 ng/mL and 7 ng/mL, with a significantly increased concentration in T2DM subjects, in whom it ranges from 6.9 ng/mL to 11.5 ng/mL [123] and positively correlates with IR [124,125]. The gene discussed is RETN; the disease is type 2 diabetes mellitus.