Protective Effect Of Tea Polysaccharides And Tea Polyphenols On Blood Glucose, Lipids And Kidney In Diabetic Rats

Diabetes has become the third largest global chronic disease following cancer andcerebrovascular diseases. Diabetes and its complications has been a serious threat to humanhealth. Currently, people have also committed to develop the natural anti-hyperglycemicagents or health food in addition to taking hypoglycemic agents and insulin injections toprevent diabetes. Tea has a long history in China, which had been known as health caredrinks since ancient times. It has been nearly30-year history for hypoglycemic effect. Theresearch confirmed the main components of tea for the treatment of diabetes and itscomplications were tea polysaccharides (TPS) and tea polyphenols (TP). However, theresearches mainly focused on tea polysaccharides or TP alone about the treatments ofdiabetes on the level of animal experiments, the synergy between them was rarely reported.Wang Linge explored synergistic effect of the TPS and TP on diabetes at the cellular level,the results confirmed the synergy of TPS and TP.Firstly, in this paper, the method of water extraction and alcohol precipitation was used toextract the TPS in rough old green tea. Then TPS had been separated and purified via anionresin. The content and their proportions of TP and TPS in the soups of green tea, oolong teaand black tea were measured following cell experiments. The rats was induced byintraperitoneal injection of STZ, then the rat models were administered with TPS or/andpolyphenols for4weeks respectively according to different ratios and doses of them inaccordance with the proportions of TP and TPS in the soups of green tea, oolong tea andblack tea. The protective effect of TPS and TP on blood glucose, lipids and kidney in diabetic rats were studied on the level of animal experiments. The main results were asfollows:1. Optimized processes of hot water extraction, ethanol precipitation, bleaching anddeproteinization were used to extract TPS and got crude TPS product. After furtherpurification of TPS through Q-Seahorse FF anion exchange column, pure TPS1and TPS2with different molecular weight were isolated. In order to improve the measure accuracy ofpolysaccharide, the standard curve was established using the purified TPS2instead ofglucose in the method of phenol-sulfuric acid. TP and TPS were measured in the soups ofgreen tea, black tea and oolong tea, the proportions of TP and TPS in green tea, black teaand oolong were close to5,3and8.2. The study of TPS and TP on blood glucose and lipid in diabetes rats showed the fastingplasma glucose (P<0.01, P<0.05) was significantly reduced by TPS and TP ratio groups(TP/TPS=3, TP/TPS=5and TP/TPS=8), and glucose tolerance (P<0.01) was improved. Thecontents of glycosylated hemoglobin and glycosylated serum protein significantly decreased(P<0.01). The TPS and TP co-ordination group TP/TPS=5had significantly improved β-cellfunction index and Insulin secretion index (P<0.01), it showed a good synergistic auxiliaryhypoglycemic effect. There were no differences between the experimental groups on serumtotal cholesterol. TP and TP/TPS=5treated groups were shown to lower the serumtriglycerides and low-density lipoprotein cholesterol, while TPS treated group increased theserum high-density lipoprotein cholesterol.3. The study of TPS and TP on kidney in diabetes rats indicated that TP/TPS=5treatedgroup significantly reduced urine glucose,24-hour urine volume (P<0.05), and kidneyhypertrophy index. The ratio groups of TP and TPS, especially TP/TPS=5treated groupseffectively improved the activity of superoxide dismutase (P<0.05), reduced the generationof malondialdehyde and relieve oxidative damage in the kidney tissue. The ratio groups of TP and TPS effectively reduced the levels of nitric oxide in the kidney tissue. To someextent the indicators investigation of hematuria also reacted the preventive of the ratio of thegroup effect on the diabetic nephropathy.4. The study of TPS and TP on blood glucose, lipids and kidney in diabetes rats showed thatthe ratio group of TP/TPS=5not only reduced the blood sugar of diabetic rats, but alsolowered renal oxidative damage to protect the kidneys. TP/TPS=5was precisely theproportion of TP and TPS in green tea soup, which also confirmed the fact that green tea asa folk prescription to treat diabetes.The purpose of this study was to explore the protective effect of TPS and TP on diabetes.It provided a basis for the treatment of diabetes as well as the comprehensive utilization oftea.