Inclusion criteria for studies were: (a) T2DM patients; (b) berberis (vulgaris/integerrima) therapy as intervention; (c) control group of placebo or metformin; (d) outcomes including fasting blood glucose (FBG) levels, glycated hemoglobin (HbA1c%), Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), fasting serum insulin (FSI), 2-h postprandial glucose (2hPPG), fructosamine, weight, and BMI; (e) randomized controlled trials (RCTs). This evidence concerns the gene INS and type 2 diabetes mellitus.