| The incidence of diabetes mellitus is rapidly increasing in all parts of the world. The World Health Organization has estimated that diabetes mellitus will affect 221 million people worldwide by 2010, and most cases (90-95%) are non-insulin dependent diabetes mellitus (NIDDM). Diabetic nephropathy (DN) is a common but serious complication of NIDDM, and it is a main cause of death in diabetic patients. Recently, the increasing interest has been attracted for development and utilization of antidiabetic plants due to their less side effects and no-drug-resistance, especially in developing countries. Lycium barbarum polysaccharide (LBP), extracted from the traditional Chinese herb Lycium barbarum, is found to have bioactivities such as anticancer, antioxidant and hypoglycemic activities. However, very little is reported about the effect and mechanism of LBP in treating insulin resistance (IR) and DN in NIDDMLBP was extracted from Ningxia-Lycium barbarum by water extraction and ethanol precipitation technique. And the ingredient of LBP-4a was obtained by separation and purification. The animal model of NIDDM was made by feeding high-glucose and high-fat diet and subjecting to.i.p.little-dose streptozotocin (STZ). The rats of NIDDM model were divided into four groups, including model group, LBP-4a low-dose and high-dose groups, rosiglitazone group and normal control group. In order to research the effect of LBP-4a on reducing blood glucose, ameliorating IR and treating DN in NIDDM rats, a lot of techniques were used such as Single Cell Gel Electrophoresis, immunohistochemical staining, ELISA, immunoprecipitation and Western blot et al. We studyed systematically the effect of LBP-4a on IR and DN in NIDDM rats and researched the mechanism from the point of view of cytokine and signal transduction. The main results were as follows.(1)LBP was extracted by the following procedure: baking, defatting, discoloration, removing small molecular sugar, deposition by ethanol, cleaning by organic solvent, removing protein by Sephadex G-200 column and vacuum drying, and so on. LBP was powder and the extraction rate was 2.58±0.14(g/100 g). Four LBP fractions, LBP-1, LBP-2, LBP-3 and LBP-4, were got by DEAE-Cellulose column with eluent of NaCl, dialysis and freeze drying respectively. One sub-fraction LBP-4a was got from the corresponding active LBP-4 fractions by Sephadex G-200 column with water as eluent. LBP-4a was identified to be homogeneous by SDS-PAGE, which showed a single band after staining with Ag. LBP-4a was a white or buff cotton-like solid. The extraction rate of LBP-4a was 1.07%.(2)After LBP-4a (high-dose) treatment for 4 weeks, body weight and the content of visceral fat mass were evidently decreased (P<0.01, P<0.05) and the level of fasting blood insulin was also significantly decreased (P<0.01). LBP-4a had glucose-lowering and lipid-lowering effects on NIDDM rats. Furthermore, LBP-4a had antioxidative function and repairing DNA damage on NIDDM rats.(3)The morphologic changes suggested that LBP-4a had protective function on pancreas, liver and kidney in NIDDM rats. It showed that the amount of pancreatic islets and cells was increased by light microscope. An electron micrograph of hepatocyte in high-dose LBP-4a treatment rats showed the nuclear membrane was distinct; the disposition of euchromatin, heterochromatin and glycogen particles is uniform. The rough surfaced endoplasmic reticulum appeared normal. The structural changes in mitochondria with severe swelling, extensive vacuolization and lipid droplets were ameliorated associated with LBP-4a. Ultrastructure of glomerulus was observed by electron microscope. The result displayed that the structure of filter membrane was intact and the foot process was thickening, but their arrangement was regularity after LBP-4a treatment Furthermore, LBP-4a could improve the phenomena of hyperplasia of intercapillary cells and thickening of glomerular basement membrane.(4)In the present study, the effective mechanism of LBP-4a on insulin resistance was investigated in NIDDM rats. It showed that LBP-4a could induce GLUT4 translocation in skeletal muscle of NIDDM rats, and the effect was related to the increase of hyper-phosphorylated PKB.(5)By Western blot and immunoprecipitation, the expression and activity of p38MAPK were detected in the skeletal muscle of NIDDM rats. It indicated that administration with LBP-4a could enhance the activity of p38MAPK in skeletal muscle of NIDDM rats, and so, LBP-4a affected the insulin signal transduction passageway. (6)The effect of LBP-4a on renal function and antioxidative activity of kidney was examined in NIDDM rats. LBP-4a significantly ameliorated diabetic renal damage and enhanced the activities of antioxidant enzymes.(7)The effective mechanism of LBP-4a on DN was investigated. The results indicated that LBP-4a treatment for 4 weeks, the membrane PKC activity was significantly decreased (P<0.01). The expression of PPAR-γmRNA and the content of PPAR-γwere significantly increased in NIDDM rats kidney treated with LBP-4a (P<0.01). By immunoprecipitation, it showed that LBP-4a could confront the increased activity of p38MAPK induced by hyperglycemia in renal tissue.In this study, the effects of sub-fraction LBP-4a on IR and DN were investigated systematically in NIDDM rats and the action mechanism was discussed from much points of view. It will provide a comprehensive and scientific evidence for development of Lycium barbarum as a suitable natural antidiabetic agent.
|
PDF Full Text Request