GLUT4 content and its activation as well as SLC2A4 gene expression level are decreased in patients with type 2 diabetes. GLUT4 -coded by SLC2A4 (17p13) is an insulin-sensitive transporter with a critical role in glucose homeostasis and diabetes pathogenesis, preferentially expressed in the adipose tissue, heart muscle and skeletal muscle. We tested the hypothesis that natural selection acted on SLC2A4.