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Objective The aim of this study was to observe the antidiabetic effect and mechanism of chitooligosaccharides (COS).Methods 1.In vivo experiment:Type 2 diabetic rats were rendered by feeding high-energy diet together with injection of streptozotocin (STZ). After 8 weeks treatment of COS, the changes on glycometabolism, insulin sensitivity, lipids, serum nitric oxide synthase (NOS), malonaldehyde content(MDA), superoxide dismutase(SOD), serum hepatic marker enzymes levels, liver and muscle glycogen content, expressions of glucose transporter GLUT-4 mRNA, MDA and SOD activity of pancreas were also observed. The pathological changes of the rats’ liver and pancreas were observed in light microscope.2. In vitro experiment:The effect of COS on pancreaticβcell (INS-1) was also examined.Results 1. In vivo experiment:The model rats established by injection STZ after feeding high glucose and lipids conformed to type 2 diabetes rats. The results showed that COS significantly reduced fasting blood glucose (FBG), fasting insulin (FINS), lipids, increased insulin sensitivity index (ISI) and improved oral glucose tolerance (P<0.05) COS increased liver glucokinase activity and glycogen content and upregulated the expressions of GLUT-4 mRNA in adipose and soleus muscle. COS also raised in the SOD activity and reduced the MDA content in serum and pancreas homogenate(P<0.05). Pancreas hematoxylin/eosin (HE) staining of diabetic rats showed ruptured islet, but changes of pancreatic islet in diabetic rats were minimized by administration of COS.2. In vitro experiment:It was found that COS played important roles in INS-1 cells by promoting proliferation, increasing glucose stimulated insulin release, upregulating the expressions of GLUT-2 mRNA and protecting against STZ-induced apoptosis (P<0.05)Conclusion The results from the present study indicate COS has protective effect for type 2 diabetes through ameliorating insulin resistance, regulating lipid metabolism, mediating antioxidation, promoting the proliferation ofβcells, increasing insulin secretion and protectingβcells.
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