Chitosan Reduces Gluconeogenesis and Increases Glucose Uptake in Skeletal Muscle in Streptozotocin-Induced Diabetic Rats

Chitosan is a natural and versatile biomaterial with a blood-glucose-lowering effect in diabetic animals, but the mechanism of action is still unknown. This study was designed to investigate the possible mechanisms involved in the hypoglycemic activity of chitosan in rats with streptozotocin (STZ)-induced diabetes. Male Sprague Dawley (SD) rats were divided into non-diabetic with cellulose (control), diabetic with cellulose (DM), and diabetic with low- (DM + LOS) and high-(DM + HCS) molecular-weight chitosan groups. After a 4 week feeding study, plasma glucose and fructosamine levels were increased while plasma leptin was decreased in the DM group when compared to the control group. These alternations caused by diabetes could be effectively reversed by both chitosan treatments. The increased gluconeogenesis-related signals including phosphoenolpyruvate carboxykinase (PEPCK) expression and phosphorylations of p38 and AMP-activated kinase (AMPK) in the livers of diabetic rats were attenuated by chitosans. Moreover, chitosan significantly increased muscle glucose uptake-related signals including Akt phosphorylation and glucose transporter-4 (GLUT4) translocation from the cytosol to membrane in the soleus muscles of diabetic rats. These results indicate that chitosan may possess a potential for alleviating type-1 diabetic hyperglycemia through the decrease in liver gluconeogenesis and increase in skeletal muscle glucose uptake and use.