Effect Of Tea Polysaccharide On Blood Glucose Islet Function In Db/db Mice

Objective： The prevalence of type-2diabetes mellitus has beenincreasing along with social development and changing lifestyle. The numberof deaths caused by diabetic complications in developed countries is ranked inthe third, following cancer, cardiovascular and cerebrovascular diseases.Medicine such as sulfonylurea, which stimulates insulin secretion, induceshypoglycemia, injures liver and kidney, fails in inhibiting the apoptosis ofpacreatic islets. Therefore, it is important to look for the natural resourceswithout hypoglycemic effect and other side effects. In recent years, effect oftea polysaccharides(TPS) in reducing blood glucose has received more andmore attention. The related research shows, TPS treat diabetes by protectingthe pancreatic islet, and improving the activity of liver gluokinase. We studiedthe effect of TPS on blood glucose, insulin secretion in vivo in db/db mice,isolated islets of mice and tested islet function in vitro.Method：The4week-aged db/db were randomly divided into five groups,provided by sterile water, metformin (200mg/kg/d) and differentconcentrations of tea polysaccharides (100mg/kg/d,200mg/kg/d,300mg/kg/d)for4weeks. db/m mice were included in control group. Water intake, foodintake and body weight were recorded weekly, respectively. Blood was takento test blood glucose、 insulin(FINS)、 alanine aminotransferase(ALT)、aspartate aminotransferase(AST) and creatinine(CRE). Pancreatic islets wereisolated by collagenase digestion methed, purified by Ficoll-400, andincubated in RPMI1640overnight.20islets were cultured in media with lowerglucose concentrations(5.6mmol/L) for1hour, then moved into media withhigher glucose concentrations(20mmol/L) for1hour. Enzyme-linkedinmunosorbert assay was used for the determination of insulin concertration.Using SPSS for statistical analysis, all data are expressed as(x士S). Results：1Results of weight：There were no significant difference in body weight among each group atthe beginning of the experiment (P＞0.05). At the end of the experiment,compared with the control group, the weight of mice in model group,metformin group and TPS groups were significantly increased（P<0.05）. Atthe end of the experiment, weight of mice in model group was higher thanmetformin group and each group of TPS(P<0.05). The body weight in the teapolysaccharide groups was higher than thai in metformin group (P<0.05),there was no significant difference among each group of TPS (P>0.05).2Results of water intake and food intake：Before the experiment，the water intake and food intake in control groupwas lower than others(P<0.05). But there was no significant differencebetween the model group、metformin group and TPS group（sP>0.05）. Afterthe experiment, the water intake and food intake of metformin and TPS groupswere decreasing along with the time(P<0.05). There was no significantdifference between metformin group and TPS groups（P>0.05）.3Results of ALT,AST,CRE：Compared with control group, the levels of ALT and AST in model group,metformin group and TPS groups were higher (P<0.05). The levels of ALTand AST in metformin group were higher than those in model group(P <0.05).Compared with metformin group、model group, the ALT and AST levels inTPS groups decreased significantly(P<0.05). There was no significantdifference among TPS group（sP>0.05）. There was no significant difference inCRE among all groups (P>0.05).4Results of blood glucose：Before the trial，the blood glucose in control group was lower than modelgroup, metformin group and TPS groups(P <0.05). During test，blood glucoseof mice in model group increased over time. Compared with model group, theblood glucose in metformin group and TPS groups decreased significantly(P <0.05). The blood glucose in TPS groups was higher than that in metformingroup(P <0.05). There was no significant difference among TPS groups (P> 0.05).5Results of fasting serum insulin (FINS)、insulin secsitivity index(ISI)、insulin resistance index(IRI)：FINS of mice in model group, metformin group and TPS groups washigher than control group (P <0.05). At the end of the experiment, comparedwith model group,the level of FINS decreased in TPS groups and metformingroup (P<0.05). FINS in TPS groups was higher than that in metformin group(P <0.05). Compared with model group, IRI was lower and ISI was higherin each TPS groups and metformin group(P <0.05). ISI in TPS groups waslower than that in metformin group(P <0.05), IRI of mice treated with TPSwas higher than that in metformin group (P <0.05). There was nosignificant difference among every TPS groups(P>0.05).6Results of islet function：Under the low glucose environment,there was no significant difference ininsulin secretion among all groups (P>0.05). In high glucose environment，insulin secretion in in control group、metformin and TPS groups was morethan that in model group (P <0.05). There was no significant differencebetween TPS groups and metformin group(P>0.05).SI of control group、metformin and TPS groups was more than that in model group (P <0.05).There was no significant difference between TPS groups and metformingroup(P>0.05).Conclusion：1Tea polysaccharide reduces the body weight of the db/db mice and decreasesthe food intake and water intake of db/db mice2Tea polysaccharide stimulates insulin secretion, improves insulin sensitivityand decreases blood glucose, the hypoglycemic effect of polysaccharide wasweaker than metformin.3Tea polysaccharide stimulates insulin secretion, improves islets function.4Tea polysaccharide reduces the liver injury of db/db mice.