INS and type 2 diabetes mellitus: We collected 102 salivary samples from four cohorts, namely, nondiabetic people (Group A, 32 samples), treatment-naïve T2D patients (Group B, 31 samples), T2D patients with metformin treatment (Group C, 17 samples), and T2D patients with combined medication treatment (Group D, 22 samples, insulin plus metformin or other hypoglycemic drugs) (Supplementary Tables 1 and 2).