Antidiabetic Effects Of Chitooligosaccharides And It's Derivatives

The diabetes mellitus (DM) is a kind of endocrine metabolism disease, having the heredity tendency caused by absolute or opposite hyposecretion of insulin. The high plasma glucose and urine glucose are it's main characteristics, which usually leads to the metabolize obstacle of sugar, protein and fat, also many organ systems have significant long-term complications in such things as, cardiovascular, cerebrovascular, retinopathy, nephropathy and neuropathy, result in the very big bane. Diabetes mellitus is a disease with high prevalence all over the world that grows almost at epidemic rates. The long-term tissue complications that affect small and large blood vessels are directly connected with the time that the patients suffer of hyperglycemia. Diabetes has become the third chronic uncontagious disease, which threatens the human health seriously after malignancy, cardiovascular and cerebrovascular problems. Chitooligosaccharides(COS) can be obtained by degradation of chitosan, which has the less molecular weight than a chitosan, it dissolves easily in water so it can be absorbed and utilized by the human body, animals and plant organisms. It has been found through research, that the chitooligosaccharides not only has familiar characteristics with chitosan,but also has the other physiology activities and pharmacological effects, such as improving the organism's immunity, regulating plasma liquid and the effects of antitumor etc. COS possess various biological activities and have a considerable potential to be utilized in diabetes mellitus applications.Being treated with acetic anhydride under homogeneous conditions,chitosan(D.D.=90%)can be used to prepare 50%,70% degree of deacetylation chitosan by controlled partial N-acetylationmethod.Then soluble chitooligosaccharides were prepared by enzymatic hydrolysis of chitosan with the chitosanase. one had the different molecular weight, and the other had the same molecular weight but different degree of deacetylation.What's more the preparations of COS-Cr,COS-VO,COS-Se had been studied. The characterization results of UV ,FT/IR, EA indicated that Cr3+,VO2+,SeO32- are attached to C2 amino and C6 hydroxyl hydroxyl group of chitooligosaccharides.In vitro,the effect of varying molecular and degree of deacetylation COS and COS-Cr,COS-VO,COS-Se on the proliferation of pancreatic islet cells and the release of insulin were detected with optical microscope,MTT colorimetric assay,radioimmunoassay methods respectively. In addition to, we studied the cytotoxicity of different samples. What's more ,the protective effect of varying molecular and degree of deacetylation COS and COS-Cr,COS-VO,COS-Se on the DNA damage of pancreasticβcells induced by streptozotocin were detected with optical microscope,MTT colorimetric assay,DNA gel electrophoresis and Comet assay methods respectively.The results manifest that varying molecular and degree of deacetylation COS and COS-Cr,COS-VO,COS-Se can stimulate the growth of islet cell which has outstanding molecular-dependence. These different molecular and degree of deacetylation samples all can stimulate the isletβcell release insulin. Our study indicate that lower molecular weight and 90% degree of deacetylation COS ,can improve the overgrowth of pancreatic isletβcells very much ,and which also leads to a increase in insulin secretion of pancreatic cells.The cytotoxicity experiment demonstrates that COS and COS-Cr,COS-VO,COS-Se is security.The results show that long time exposure to STZ is capable of causing a significant increase in DNA damage levels. Conversely, no induction of DNA damage was observed in lower molecular weight and 90% degree of deacetylation COS treated group(500 mg·L-1) in vitro treatment of NIT-1 cell lines. Similar differences in DNA damage between other COS groups and positive control group were observed after treatments with STZ ,2mM . The results indicate that the lower molecular weight and 90% degree of deacetylation COS has prominent protective effect on the NIT-1 cells induced by STZ and can prohibit the apoptosis of NIT-1 cells.The diabetic model of Wistar rats was duplicated with STZ once intraperitoneally(65mg·kg-1), then divided into diabetes treating groups ,diabetes control groups and normol groups randomly. The diabetes treating groups were administered (ig) chitooligosaccharides at dose of 250,500,1500 mg·kg-1 daily for successive 60d. Each group measured the plasma glucose every 10 days. after 60 days feeding study:①oral glucose tolerance test was examined;②the effects of COS on regulating plasma lipid and antioxidant ability of DM mouse were measured ,the index about the function of kidney,liver in plasma and urine were evaluated;③weight of pancreas,thymus,spleen,liver,kidney were measured and calculated the coefficient of organs;④pancreas,liver,kidney and muscle were examined by pathlogic methods;⑤The hepatic and muscular glycogen levels were detected by anthrone;⑥the intestinal flora were cultured,calculated and identified,the counts of B/E were also calculated.All dose of chitooligosaccharides have effective effects on the general clinical symptom of DM rats,decrease the 2hPG and urine glucose, normalize the disorders of glucose tolerance.Chitooligosaccharides of 500 mg·kg-1 daily decrease the plasma glucose to 16.14mmol·L-1,the decrease rate is 47.48%,and the AUC (Areu Under Curve) in oral glucose tolerance is merely 68.69%, compare with DM group have significant difference(P<0.01).All dose of chitooligosaccharides improve the capability of T-AOC and activity of SOD,decrease the content of MDA drastically, and have significant difference(P<0.01)compare with DM group. All dose of chitooligosaccharides decrease the level of TG,ApoB and A/B, have significant difference compare with DM group. High and middle dose of chitooligosaccharides decrease the level of BUN,ALT,AST,TBIL,IBIL,NAG in plasma and BUN/Cr,TP/Cr,NAG/Cr in urine,increase the level of TP,ALB,GLO,A/G,AST/ALT, compare with DM group have significant difference. All dose of chitooligosaccharides have protective effects on the pancreastic islet,kidney,liver,increase the coefficient of pancreas and decrease the coefficient of kidney and liver. Morphological investigation on pancreas show different dose of chitooligo saccharides had different effects on the reduction of islets,loss of pancreastic cells,nuclear pyknosis of pancreastic cells,etc. The normal liver structure and abundant glycogen are observed in the treatment group .There are obvious liver fatty degeneration and little or no glycogen in diabetes group. After administration with chitooligo- saccharides,the numbers of Bifidobacteria and Lactobacillus increase significantly,but the numbers of pathogenetic E.coli and Enterococcus decrease significantly, compare with DM group.The counts of B/E also increase significantly accordingly.In conclusion, chitooligosaccharides has effective effects on the general clinical symptom, 2hPG and urine glucose, disorders of glucose tolerance, regulating plasma lipid and improving antioxidant ability , normalize the index about the function of kidney and liver in plasma and urine, protecting the pancreastic islet,kidney and liver of DM rats. The effects of increase the glycogen storage of liver and muscle, maybe one of the mechanism about chitooligosaccharides'effects on decreasing the plasma glucose.