Effects Of Chitosan Derivertives On Blood Glucose Regulation In Diabetic Mice

Diabetes mellitus is a common metabolic disorder characterized by chronichyperglycemia which is caused by insufficiency of insulin secretion relatively orabsolutely and characterized by polydipsia, polyphagia, polyuria and weight losssymptoms. Diabetes mellitus has the heredity tendency.Chitin is an N-acetyl-D-glucosamine polysaccharide and is widely found incrustaceans or insects （such as shrimp and crabs） and fungi （yeasts, molds, etc.）.Chitosan is a deacetylation product of chitin with a variety of biological activity and awhite amorphous, translucent solid with slightly pearly luster. Modifying themolecular structure of chitin and chitosan can improve their performance and obtaindifferent structures of water-soluble chitosan derivatives which can meet specificneeds. Degradation of high molecular weight chitosan can obtain low molecularweight chitosan products which have a better water-soluble and a broader applicationvalue than chitosan. It is more conducive to the body’s absorption and utilization.In this research,50%D.D. chitosan （CTS）, sulfonated chitosan （S-CTS） andcarboxymethyl-chitin （CMC） were prepared by chemical synthesis and enzymaticdegradation of high molecular weight chitosan. The structure of three chitosanderivatives were detected.In vivo, type Ι diabetic mices were successfully induced by single intraperitoneal injection of steptozotocin （STZ）. All of the diabetic rats were randomly divived into the normal control and model control group which were fed with a certain volume of distilled water. CTS, SCTS and CMC treating groups were administered respectivelyat dose of200mg/kg CTS, SCTS and CMC daily for continuous45days. Fastingplasma glucose （FPG） and fasting glucose tolerance （FGT） were measured after45days, as well as body weight, triglyceride （TG）, high density lipoprotein cholesterol（HDL）, total cholesterol （TC）, organ index of liver, spleen, kidney and pancreas.Pancreas, liver and kidney tissue of rats were exanimated histologically.In vitro, the effects of three chitosan derivertives on the proliferation of pancreatic βcells were detected with MTT colorimetric assay. RIN-m5f islet cell lines werecultured by conventional cell culture. The chitosan derivatives were seted5concentration gradients （62.5mg/L,125mg/L,250mg/L,500mg/L and1000mg/L）, and the blank control group was seted. The proliferation of cell was detected at48h,96h and144h respectively, and the proliferation rates of cells were calculated byA/A₀×100%. The experiment was repeated three times.The experiment results were as follows:1. Physical and chemical properties of CTS, CMC and SCTS are as follows:moisture contents are5.9%,5.47%and5.64%respectively, ash contents are1.06%,1.09%and18.736%respectively and degree of deacetylation are48.53%,10.23%and37.53%respectively. D.S. of CMC is98.65%and sulfonation degree of SCTS is88.3%. All three samples are water-soluble. The infrared spectroscopy results are asfollows: characteristic absorption peaks of CTS are at3440cm^-1,1650cm^-1,1557cm^-1,1071cm^-1, characteristic absorption peaks of CMC are at3443cm^-1,1649cm^-1,1417cm^-1,1069cm^-1-1, and characteristic absorption peaks of SCTS are at1232cm^-1,799cm^-1.2. Three samples had different effects on improving glucose metabolism after45days of feeding study. Compared with DM model group, all chitosan derivertivescould decrease the FBG, in which CTS group and CMC group have significantdifferences （P＜0.05） after30d and very significant differences （P＜0.01） after45d.Hypoglycemic rates of them are3.74%and4.88%respectively. Damaged glucosetolerance of three experimental groups are all effectively repaired after45days, inwhich each phase blood glucose levels （PG） are reduced at different degrees.Compared with DM model group, AUC of CTS group and CMC group have verysignificant differences （P＜0.01） after45d and the effect of CMC is best.Compared with DM model group, three experimental groups have effects ondecreasing TC and increasing HDL, in which CMC have very significant differences（P＜0.01） and SCTS have significant differences （P＜0.05）.The results of tissue observation and the determination of organ index in diabeticrats showed that three chitosan derivatives have protect effects on the islet, liver andkidney of diabetic rats to different degree.3. The results of cell experiments showed that optimum concentrations of CTS,CMC and SCTS are500mg/L,250mg/L,500mg/L respectively. In the optimumconcentration, the proliferation rates are154.1%,195.8%and163.1%respectivelyafter144h. CMC have the best effect. CMC could decrese the blood glucoseobviously in animal and had effects on repairing damaged cells of pancreasin tissue observation. The results are consistent with the results of cell experiments andindicate that CMC may have effects of protecting pancreas and repairing the damagedislet cells. Its mechanism needs further study.