The present study was designed to investigate the effects of sitagliptin on metabolic parameters as well as the expression levels of retinol-binding protein 4 (RBP4) and glucose transporter type 4 (GLUT4) in a rat model of type 2 diabetes mellitus. A rat model of type 2 diabetes mellitus was established by a combination of a high-fat diet and intraperitoneal injection of low-dose streptozotocin. Rats were divided into three groups: normal control group, diabetes group, and diabetes + sitagliptin group. Body weight, glycemic parameters, lipid profiles, fasting insulin (FINS) and serum RBP4 levels were assessed at baseline and after 6 weeks of therapy. Western blotting was used to detect the tissue RBP4 and GLUT4 expression levels. After treatment for 6 weeks, the diabetes + sitagliptin group displayed significantly improve levels of blood sugar, blood grease, and insulin sensitizing functions (P < 0.05) than the diabetes group. Sitagliptin markedly down regulated RBP4 expression levels and up-regulated GLUT4 expression levels in adipose tissue and skeletal muscle. The results indicate that sitagliptin can modulate the RBP4-GLUT4 system in adipose tissue and skeletal muscle. Modulation of the RBP4-GLUT4 system may be one of the mechanisms by which sitagliptin ameliorates the symptoms of type 2 diabetes mellitus.
Keywords: GLUT4; RBP4; Sitagliptin; type 2 diabetes mellitus.