Hypoglycemic Effect Of Polysaccharides Extracted From Ulva Pertusa Kjellm In Alloxan-induced Diabetic Mice And Its Mechanism

To study the hypoglycemic effects of polysaccharide extracted from Ulva pertusa Kjellm indiabetic mice induced by the alloxan and to explore the hypoglycemic mechanism of Ulvapertusa Kjellm polysaccharide. The polysaccharide was extracted by hot water and precipitatedby ethanol from Ulva pertusa Kjellm. The experimental diabetic mice were randomly dividedinto four groups: low and high dosage of polysaccharide (250and1000mg/kg body weight),positive control group (metformin at1000mg/kg body weight) and the diabetic model controlgroup which were administrated with saline. At the same time, the general mice were divided asnormal control group and were administrated with saline. After28d, the concentrations of bloodglucose, lipid, serum insulin, G-6-PD and hepatic glycogen, GCK, G-6-Pase was determined aswell as the activity of SOD, GSH-Px and CAT and the content of MDA in liver and kidney. Inaddition, the histological pathology of pancreas was observed by using HE staining. The resultsare shown as follows:1. The effects of polysaccharide extracted from Ulva pertusa Kjellm on glucose and lipid levelsin diabetic mice.The polysaccharide extracted from Ulva pertusa Kjellm had a significant hypoglycemiceffect on alloxan-indued diabetic mice after two weeks (P<0.05), and the effect of high dosepolysaccharide (1000mg/kg·d) was the most remarkable which was prior to the effect ofmetformin. The Ulva pertusa Kjellm polysaccharide not only improved polydipsia, polyphagia,polyuria, which are caused by diabetes, but also antagonized enlargement of liver and kidney andatrophy of thymus and spleen in diabetic mice. It indicated the polysaccharide has the certainprotective function on the tissues and organs of diabetes mice. Compared with the diabetic mice,the polysaccharide of Ulva pertusa Kjellm (250、1000mg/kg·d) and metformin significantlydecreased the contents of TG, TC and BUN (P<0.05).2. The effects of polysaccharide extracted from Ulva pertusa Kjellm on glucose metabolism indiabetic mice.The polysaccharide of Ulva pertusa Kjellm significantly enhanced insulin levels of diabeticmice (P<0.05), but did not affect those of positive control group and diabetic model controlgroup. As compared with diabetic model control group, the activities of hepatic GCK andG-6-PD were increased significantly, but the activity of hepatic G-6-Pase was decreased significantly in polysaccharide group (P<0.05). Metformin had a similar effect on hepaticG-6-PD and GCK, however, no effect on hepatic G-6-Pase activity in diabetic mice treated group(P>0.05). The content of liver glycogen was significantly decreased in diabetic model controlgroup, however, the polysaccharide and metformin groupd showed a significant increase inhepatic glycogen content (P<0.05).3. The effects of polysaccharide extracted from Ulva pertusa Kjellm on antioxidant capacity indiabetic mice.As compared with diabetic model control group, the activities of SOD, GSH-Px and CAT inliver and kidney were increased significantly in polysaccharide group and positive control group(P<0.05), but the content of MDA was decreased significantly (P<0.05). This suggested that thepolysaccharide of Ulva pertusa Kjellm could improve the antioxidant capacity of liver andkidney on diabetic mice to some extent. The histological pathological examination showed thatthere were some serious damages in cell morphology and construction of pancreas in diabeticmice, however, polysaccharide administration ameliorated this response. It indicated that thepolysaccharide of Ulva pertusa Kjellm could protect pancreatic islet from injuring to a certaindegree.In conclusion, the polysaccharide extracted from Ulva pertusa Kjellm showed a promisinghypoglycemic effect, improved polydipsia, polyphagia, polyuria and lipid metabolism disordersignificantly, which are caused by diabetes. The primary hypoglycemic mechanism mayberelated to following approach:1) to strengthen the antioxidant capacity, relieve the oxidativelesion of islet, protect the islet cell from injuring, promote the injured pancreatic islet to restoreand enhance the exudation of insulin.2) to regulate certain key carbohydrate metabolic enzymeactivities, improve ingestion and absorption of glucose and promote the conversion of bloodglucose into glycogen, therefore reduce blood glucose. Our study provided a strong theoreticalsupport that the polysaccharide extracted from Ulva pertusa Kjellm could act asantihyperglycemic food and medicine against the complications of diabetes.