Antidiabetic Activities, Isolation,Purification And Structure Research Of Mori Fructus Polysaccharides

Objective: Type 2 diabetes mellitus(T2DM) is becoming a serious threat to human health. The fruit of Morus alba L. is widely used as a traditional Chinese medicine to treat dizziness, tinnitus, insomnia and premature graying, protect the liver and kidney, and also used to treat diabetes mellitus. And also M. alba fruit is a kind of popular fruit all over China. Many researches demonstrated that water extract from root bark, leaves, and ramulus of mulberry such as polyphenols and polysaccharides, have antihyperglycemia and antihyperlipidemia effects. The aim of this study was to evaluate the antidiabetic activities of polysaccharides from M. alba fruit on T2 DM rats and discover the possible mechanism of these activities. In addition, by the separation and purification of active polysaccharide parts, to get high purity polysaccharides, and to study its structure, for the study of structure-activity relationship of polysaccharides from Morus alba fruit.Material and methods: Diabetic rats treated with two fraction of M. alba fruit polysaccharides, MFP50 and MFP90, were studied which were induced by high-fat diet and streptozotocin, compared with normal rats and metformin treated diabetic rats. After 7 weeks treatment, the fasting blood glucose(FBG), oral glucose tolerance test(OGTT), fasting serum insulin(FINS) levels, homeostasis model of assessment-insulin resistance(HOMA-IR), levels of glycated serum protein(GSP), serum alanine transaminase(ALT), serum lipid profiles, antioxidant capacity in liver and histopathological change of pancreas were measured. After that, the expression of insulin receptor(InsR) and insulin receptor substrate-2(IRS-2) were measured by Western Blot Analysis to probe the possible mechanism of antidiabetic activities. Then we purify active polysaccharides by DEAE cellulose, DEAE Sepharose, and Sephadex column chromatography to obtain pure polysaccharides, and laid the foundation for the structure-function relationship research of them.Results: After 7 weeks of treatment, in the group treated by MFP50, the level of FBG, oral glucose tolerance test-area under the curve(OGTT-AUC), FINS, HOMA-IR, ALT and triglyceride(TG) were reduced significantly. In MFP90 group, the level of FBG, OGTT-AUC, FINS, HOMA-IR, GSP, and triglyceride(TG) were reduced significantly. Meanwhile, the level of high-density lipoprotein cholesterol(HDL-c) and the proportion of HDL-c in total cholesterol(TC) was significantly increased in MFP50 group. Moreover, MFP50 and MFP90 can restore the impaired pancreas tissues in diabetic rats. The hypoglycemic effect of MFP50 is more stable than MFP90, while the hypolipidemic effect of MFP90 is slightly better than MFP50. Moreover, the expression of InsR and IRS-2 in MFP90 group was significantly increased compared with T2 DM group. On the other hand, we basically studied the chemical constituent of MFP50 and MFP90. Through the separation and constituent analyses, we found that constituent of MFP50 and MFP90 is quite complicated. MFP50 contain at least 10 kinds of polysaccharides, and MFP90 contain at least 3 kinds of polysaccharides.Conclusion: MFP50 and MFP90 have markedly antihyperglycemic and antihyperlipidemic effects, and can relieve diabetes symptoms evidently in T2 DM rat model. M. alba fruit polysaccharides maybe become potential outstanding medicine to cure T2 DM. The structures research of M. alba fruit polysaccharides responsible for the biological activities are in progress, and the mechanisms of the antidiabetic effects are also in progress. However, by now, the methods we utilized cannot obtain sufficient pure polysaccharide to study their structure.