Study On The Hypoglycemic Activity Of Polysaccharides Isolated From Portulace Oleracea L.

Diabetes mellitus is found in all parts of the world and is rapidly increasing in most parts of the world. The World Health Organization has estimated that by the year 2025 diabetes will affect 33 million people worldwide, and most cases (90-95%) as non-insulin dependent diabetes mellitus (NIDDM). The treatment of diabetes mellitus has spent vast amounts of resources in all countries. Recently, the increasing interest has been attracted for development and utilization of antidiabetic plants because they have less side effects and no-drug-resistance, especially in developing countries.Portulaca oleracea L. polysaccharide (POP), extracted from the traditional Chinese herb Portulaca oleracea L., is found to have bioactivities such as anticancer, antioxidant and hypoglycemic activities. However, very little is known about the effect of Portulaca oleracea L. in treating insulin resistance of NIDDM and preventing or delaying the onset of diabetic complications.POP was extracted from Portulaca oleracea L. by water extraction and ethanol precipitation technique. And the ingredient of POP was obtained by separation and purification. The animal model of NIDDM was estabilshed by high-glucose and high-fat feeding combined with the injection of small-dose streptozotocin (STZ). The mouse of NIDDM model were divided into four groups, including model group, POP low-dose and high-dose groups, rosiglitazone group and normal control group. In order to research the effect of POP on reducing blood glucose, ameliorating insulin resistance and renal protection in NIDDM mouse, the techniques of Single Cell Gel Electrophoresis, immunohistochemical staining and Western blot were used to investigate the mechanism. For the first time, we studyed the effect of POP on IR and researched the mechanism from the point of view of cytokine and signal transduction. The main results are as follows:1. POP was extracted by the following procedure: deposition by ethanol, cleaned by organic solvent and vacuum drying, and so on. The content of POP was 17.04%.2. After POP (high-dose) treatment for 4 weeks, body weight and the content of visceral fat mass were evidently decreased and the level of fasting blood insulin was also significantly decreased. POP had glucose-lowering and lipid-lowering effects on NIDDM mouse. Furthermore, POP had antioxidative function and repair DNA damage on NIDDM mouse.3. By Western blot, the expression of PKB protein was increased significantly in POP-treated diabetic mice kidney (P <0.05).4. By immunohistochemical staining to investigate the mechanism of POP effect on NIDDM, the results indicated that POP treatment for 4 weeks, the PKC activity was invariably(P >0.05).The content of PPARγwas significantly increased in NIDDM mouse kidney treated with POP.Conclusions: The study investigated POP effect on insulin resistance in NIDDM mouse systematically and discussed the action mechanism from much point of view. It provided comprehensive,scientific evidence for development of Portulaca oleracea L. as a suitable dietary natural antidiabetic agent.