Research On The Mechanisms Of Radix Astragali Against Damdages Caused By High Level Of Glucose

Diabetes mellitus is a metabolic disease featured by chronic elevation of blood glucose level. The prevalence of diabetes is increasing and has become the most challenging health problem in the 21st centrury. Worldwidely, diabetes affected the health of 2300 million people, and the number is estimated to shoot up to 3500 million by 2025. Diabetes is top 4 death cause for the whole population at present, there will be one person dead because of diabetes related disease every 10 second. In America, it is estimated that more than 20 million people have diabetes, among therm 14 million people are diagnosed, 6 million people are not. Persistent high level of blood glucose attacks microvessel and macrovessels along the body. In developoing countries, diabetes is the main cause for adult blindness, visioin damage, non-trauma amputation and kidney failure. Diabetes threatens the vision, the patients with diabetes develop cataract earlier and the chances to develp glaucoma doubles, diabetes is also a major cause for delayed wound healing.In the mechanisms of diabetes complication, oxidative stress plays an important role.Oxidative stress comes from glucose autooxidation, Fenton reaction, advanced glycation end products, polyol pathway, mitochondria respiratory chain deficiency, hexasine, peroxisome, nitric oxide synthase and NADPH oxidase. Pancreaticβcells are more sensitive to oxidative stress because the level of antioxidase, such as catalase, glutathione peroxidase and superoxide dismutase inβcells is very low, which results in the weaker ability to resist oxidative stress. Oxidative stress can damage pancreaticβcells and induce the insulin secretion obstacles, moreover cause the development of complications by inducing pathologic metabolic pathways.Due to the important role of oxidative stress in the development and progression of diabetes complications, it is necessary to explore the effects of antioxidative agents on the process and progression of diabetes, especially traditional Chinese medicine, so the present study is to explore the therapeutic effects of Radix Astragali on diabetes mellitus and its mechanisms of actions through animal and cell experiments. In animal experiments, Wistar rats were injected STZ at the dose of 50 mg?kg-1 to establish diabetes rat model, the blood sugar level were tested three times on day 3, 5, and 7, those which had blood sugar level more than 16.7 mmol?L-1 three times were determined diabetes rats. The diabetes rats were classified into diabetes grou, DM and Radix Astragali group, RA; rats in DM group were given 3.3 ml/kg saline and RA group 3.3 ml/kg RA every day through IP. Normal rats were in control group, C.Blood samples were collected on day 7, 14, 30, 60 of RA injection to test the level of triglyceride(TG), high density lipoprotein(HDL-C), low density lipoprotein(LDL-C) and insulin, each time 5 rats from each group including normal rats.Human umbilical vein endothelial cells were used to explore the protective effects of RA against high level of glucose. ECV 304 cells were exposed to high glucose concentration (35mM), high glucose concentration and RA(35mM glucose and 500μg/ml), an osmetic control was set up by mannitol(25Mm). The cells were collected 24 hours later after the glucose, mannitol and RA were added to the cells, cell membrane fluidity, intracellular Ca2+ concentration, mitochondrial membrane potential, ROS production and morphology under electronic microscope were tested.On day 7 and 14 of RA injection, there was no significant difference in blood index in rats between RA and DM group(P>0.05); On day 30 and 60 of RA injection, the level of HDL-C and insulin in rats of RA groups was significantly higher than that of DM group(P<0.05), the level of LDL-C, TG, and TC lower(P<0.05).On day 7, 14 and 30 of RA injection, there was no significant difference in the morphology of liver, kidney and heart between RA group and DM group rats, which were similar to the normal rats. On day 60 of RA injection, the morphology of liver and heart in rats of RA and DM groups was similar to normal one. But in kidney and pancreas, remarkable changes were seen, for rats in DM group, glomeruli capsular spaced were narrower, matrix hyperplasia, cell number increased while for rats in RA group, the morphology of kidney was similar to that of normal rats.In cell experiment, intracellular calcium concentration was significantly higher in the presence of high glucose concentration when compared with normal, RA and mannitol control; there was significant decrease in intracellular calcium concentration in the presence of combined high glucose concentration and RA compared to mannitol control (P<0.05). Cells exposed to high glucose concentration had lower mitochondrial membrane potential compared to normal control, RA and mannitol control(P<0.05), cells exposed to combined RA and high glucose concentration had higher mitochondrial membrane potential compared to mannitol control(P<0.05).There was a significant increase in the number of apoptotic cells in the presence of high glucose concentration compared to normal control, RA and mannitol control(P<0.05), there was a significant decrease in the number of apoptotic cells in the presence of RA and high glucose concentration compared to mannitol control. Cellls exposed to high glucose concentration had higher level of MDA, OH- , O2- and lower level of SOD,CAT,GSH activities compared to normal control, RA and mannitol(P<0.05), Cells exposed to combined RA and high glucose concentration had lower level of MDA, OH, O2- and higher level of SOD, CAT, GSH activities compared to mannitol control(P<0.05). Cells exposed to mannitol had lower level of MDA, OH-, O2- and higher level of SOD, CAT, GSH activities compared to high glucose concentration(P<0.05). Under electronic microscope, the cells exposed to high glucose concentration were abnormal with swollen mitochondria and decrease in the number of mitochondria, and cristae disappeared, while the cells exposed to combined RA and high glucose concentration had normal structure and number of mitochondria with clear cristae.The results of the present research indicated that Radix Astragali could produce therapeutic effects on diabetes rats and one of the mechanisms of action was its ability to eliminate free radicals and participation in the lipid metabolism of diabetes rats.