It has been shown that dietary cyanidin-3-glucoside-riched purple corn significantly reduces blood glucose concentration and enhances insulin sensitivity in type 2 diabetic mice by upregulating the glucose transporter 4 (Glut4) and downregulating retinol binding protein 4 (RBP4) in the white adipose tissue [14]. The gene discussed is RBP4; the disease is type 2 diabetes mellitus.