| ObjectiveTo evaluate the best method for establishing insulin resistance rat model and investigate the phamarcological effects and related mechanism of Rehmannia glutinosa oligosaccharide(ROS) on glucose metabolism in insulin resistance rat model.MethodsExperimental insulin resistance rat model was induced by high lipid food,DEX at the dose of 1 mg·kg-1by intraperitoneal injection(i.p.)every other day,and both high lipid food and low dose(1mg·kg-1)of DEX by intravenous injection(i.p.)every other day,respectively.Then fasting blood glucose,body weight and glucose tolerance test were used to evaluate the best method for inducing insulin resistance rat model.Body weight,plasma glucose,hepatic glycogen, muscle glycogen,plasma lipids,free fatty acid,weights of internal organsas as well as insulin and its counter-regulatory hormone levels(glucagons and corticosterone)were also determined.According to the purpose of the experiment,insulin resistance model induced by both high lipid food and DEX(1 mg·kg-1,i.p.every other day)in rats was used in the pharmacologioal experiment.The rats were divided into control group,insulin resistance model group,ROS(100, 200 mg·kg-1·d-1)treated group and rosiglitazone(3.4 mg·kg-1·d-1)treated group.All drugs were adiministered by intragastric administration(i.g.).The rat's fasting blood glucose,glucose tolerance test,hepatic glycogen and muscle glycogen's content,plasma FFA level,plasma insulin leve were determmined.Then the mRNA expressions of adiponectin gene related to insulin sensitivity were detected by reverse transcription PCR(RT-PCR).ResultsInsulin resistance rat model can be induced by both high lipid food and low dose of DEX(1 mg·kg-1,i.p.every other day),the fasting blood glucose of this model(7.7±0.7 mmol·L-1)was increased 15.1%compared with that of control group(6.5±0.6 mmol·L-1)in 2 weeks;blood glucose increased obviously in glucose tolerance test.After intraperitoneal injection of glucose, plasma glucose level of the model group at the time of 30 min,60 min and 120 min(29.2±1.4 mmol·L-1,27.1±3.0 mmol·L-1and 19.1±3.0 mmol·L-1)was increased 108.57%,185.26%and 105.38%,respectively,compared with that of control group(14.0±4.2 mmol·L-1,9.5±2.5 mmol·L-1and 9.3±1.3 mmol·L-1);plasma lipids level was accordant with the changes of high FFA(free fatty acid)level(329.77±121.31 mmol·L-1)with 62.98%of increase compared with that of control group(202.34±43.63 mmol·L-1);hepatic glycogen and muscle glycogen's content were also increased;insulin level of the model group(72.12±12.30μIU·ml-1)was increased 251%compared with that of control group(20.54±8.88μIU·ml-1);the weights of the live and kidney were increased and that of thymus was decreased.In the study of pharmacological effets of ROS on insulin resistance in vivo,plasma glucose level in ROS treated group was decreased,plasma glucose level of the high dose of ROS treated group(7.1±1.0 mmol·L-1)was decreased 11.25%compared with that of model group(8.0±0.9 mmol·L-1).In addition,plasma glucose level was decreased in glucose tolerance test,plasma glucose level in the high dose of ROS treated group(21.7±2.5 mmol·L-1,18.4±2.9 mmol·L-1and 12.3±2.6 mmol·L-1)decreasd 17.49%,23.01%and 34.92%,respectively,at the time of 30 min, 60 min and 120 min after injection compared with that of model group(26.3±2.5 mmol·L-1, 23.9±3.0 mmol·L-1and 18.9±3.8 mmol·L-1).ROS could also decrease plasma glucose level in the insulin tolerance test.The related mechanism was invistigated and the results showed that:(1)ROS could decreased the content of hepatic glycogen and muscle glycogen;(2)The activity of glucokinase in the high dose ROS treated group(8.29±1.87 U·gprot-1)was increased 39.56%compared with that of insulin resistance model group(5.94±1.92 U·gprot-1);(3)Plasma FFA level in the high dose of ROS treated group(1245.03±505.06 mmol·L-1)was decreased 55.10%compared with that of insulin resistance model group(2126.83±834.91 mmol·L-1);(4)ROS treated group had the tendence of decreasing insulin and corticosterone levels.The insulin level in the high dose of ROS treated group(31.40±7.85μIU·ml-1)was increased 39.56%compared with that of insulin resistance model group(50.99±13.00μIU·ml-1);(5)The tendency of increasing the organ index of thymus gland,liver and kidney was showed;(6)Some damages in pancreas in the pathological examination had been repaired by the treatment of ROS in insulin resistance rats;(7) ROS can increase the mRNA expressions of adiponectin gene.ConclusionInsulin resistance model was successfully induced by both high lipid food and low dose of DEX in rats,with the characteristics of stabile plasma glucose,low release rate,similar changes of plasma lipids to that of insulin resistance in human being and good maintenance compared with insulin resistance model induced by DEX or high lipid food singly.The plasma glucose level and plasma FFA level in ROS treated groups were decreased compared with that of insulin resistance model group.The pharmacological mechanism may be related to the decrease of hepatic glycogen level,plasma insulin level,the improvement of pancreas functions,the increase of activity of GK and the increase of the mRNA expressions of adiponectin genes.
|
PDF Full Text Request