Long-term effects of chitosan oligosaccharide in streptozotocin-induced diabetic rats

Streptozotocin has been used to induce an experimental model for diabetes to study the activity of anti-diabetic agents. The cholesterol-lowering effect of chitosan makes a continued issue in the field of diabetes, but the hypoglyecemic effect is inconclusive to date. Unlike chitosan, the water soluble chitosan oligosaccharide may possess various biological properties for diabetes. The present study was designed to investigate the long-term effects of chitosan oligosaccharide in normal and streptozotocin-induced diabetic rats using glycated hemoglobin and C-peptide. Chitosan oligosaccharide feeding did not cause any harmful effect on plasma glucose as well as plasma lipid metabolism in normal rats, although slightly elevated triglyceride was observed. As compared with the diabetic control rats, effects of chitosan oligosaccharide for 12 weeks in the diabetic rats were summarized as follows; (1) the blood glucose concentrations fell significantly and it was confirmed by decreased glycated hemoglobin, (2) the plasma C-peptide was increased and provided elevated degree of insulin secretion, and (3) relatively well reconstructed pancreatic islet with β-cells and additional insulin-immunolabeled cells in the pancreatic acinus and in the intercalated duct were observed. These results suggested that chitosan oligosaccharide could improve the altered blood glucose metabolism in the diabetic rats by various mechanisms such as accelerated proliferation or neogenesis of β cells and increased secretory capacity of insulin.