BACKGROUND: Non-enzymatic glycation of proteins is involved in the complications of diabetes mellitus. Previous experiments have demonstrated that total flavones of buckwheat flower (TFBF) could improve carbohydrate tolerance. However, it is little known whether TFBF inhibit the non-enzymatic glycation of proteins.OBJECTIVE: To investigate the influences of TFBF on the non-enzymatic advanced glycation end products (AGEs) of proteins in vivo and in vitro.DESIGN: Completely randomized controlled trial.SETTING: Department of Pharmacology, North China Coal Medical College.MATERIALS: Totally 75 adult SD rats , of clean grade, weighing (200±20) g, including 38 female rats and 37 male rats, were provided by the institute of experimental animals, Chinese Academy of Medical Sciences (Certification No. SCXK11-00-0006). TFBF was extracted by our laboratory from flowers of buckwheat. The blood glucose kit was purchased from Beijing Biosino Biotechnology Company Ltd. Penicillin (Batch No.031020, 8×105 U) and streptomycin (Batch No. 030920, 1×106 U) were purchased from North China Pharmaceutical Company. Streptozotocin and BSA were purchased from Sigma Company. Fructosamine kit was purchased from Nanjing Jiancheng Bioengineering Institute, and the other chemicals were analytical pure produced domestically.METHODS: This experiment was carried out in the Department of Pharmacology, North China Coal Medical College from March to October 2004.In the first experiment, in vivo macromolecular AGEs was measured: ①Modeling and grouping: Rats were divided into 3 groups according to body mass: Normal control group (n=15), the rats were treated with 8 mL/kg normal saline intraperitoneally. Streptozotocin-treated group (n=45), the rats were fasted for 16 hours and then treated with 80 mg/kg streptozotocin of 8 mL/kg intraperitoneally. Twenty-two hours later, the blood of all rats was harvested from vena caudalis to measure the level of blood sugar.Those with fasting blood glucose ≥ 15 mmol/L were acted as diabetic rats.Streptozotocin-treated group were divided into 3 subgroups, 15 rats in each subgroups. Each rat was given intragastric administration of 0.1, 0.2 and 0.4 g/kg TFBF. Model group (n=1S): Rats were only treated with 80 mg/kg streptozotocin of 8 mL/kg . The rats in normal control group and model group were given the same volume of salt water. The administration was once a day for 12 weeks successively. ②Measurement of fasting blood glucose: After the last administration, the rats of streptozotocin-treated group were fasted for 12 hours and the blood was harvested from vena caudalis. The fasting blood glucose was measured by glucose oxidase method. ③The levels of blood plasma and nephridial tissue fructosamine and macromolecular AGEs were measured: The rats of each group were anesthetized with ethyl ether on the second day following the last administration. Blood was chosen from carotid artery, and plasma was separated.Kidneys were taken at the same time, prepared into 100 g/L tissue homogenate and centrifuged at low temperature. The levels of fructosamine in plasma and the supernatant fluid of kidney homogenate were measured according to the instructions of the kit. AGEs in plasma and renal tissue were determined by fluorospectrophotometer. The products of macromolecular AGEs were calculated. In the second experiment, in vitro macromolecular AGEs were measured as below: 0.01, 0.05, 0.10 mg/L TFBF of 6 mLrespectively was prepared with solution A (0.2 mol/L glucose, 2×l06 U/Lpenicillin, 2×106 U/L streptomycin , PBS containing 20 g/L bovine serum albumin). Control groups were set: ① without TFBF, ② without TFBF and glucose, ③ without BSA, ④ without glucose. Five parallels of each sample were sterilized by filtration and incubated in the attemperator at 37 ℃. The fluorescence of AGEs (F) in the culture was determined at the 4th, 8th and 12th weeks. Inhibition ratio (IR) was calculated and the inhibition of TFBF on AGEs was observed.MAIN OUTCOME MEASURES: In the first experiment, the levels of fasting blood glucose, fructosamine in kidney and plasma, and AGEs were measured. In the second experiment, the inhibition of TFBF on AGEs in vitro was measured.RESULTS: In the first experiment, 75 rats were involved, and 56 successful rats entered the stage of result analysis. The levels of blood glucose,fructosamine in kidney and plasma of rats in the model group were significantly higher than those of rats in the normal control group (t=7.572,10.186, 5.794,P ＜ 0.01 ). The level of blood glucose of rats in the 3 subgroups was significantly lower than that of rats in the model group (t=3.357,4.382,3.938,P ＜ 0.05-0.01); The levels of fructosamine in kidney and plasma of rats in the 0.2 and 0.4 g/kg TFBF groups were significantly lower than those in the model group (t=5.109, 4.605, 3.731,3.097,P ＜ 0.05-0.01 ). The levels of AGEs in plasma and kidney of rats in the model group were significantly higher than those in the normal control group (t=6.463, 12.704,P ＜ 0.01 ), while the levels of AGEs in plasma of rats in the streptozotocin-treated group were similar to those in the model control group (P ＞. 0.05), and those in kidney of rats in the streptozotocintreated subgroups were significantly lower than those in the model group (t=9.845, 12.799, 12.899,P ＜ 0.01 ). In the second experiment, the level of macromolecular AGEs of each group was gradually increased with ime.TFBFcould inhibit the formation of macromolecular AGEs in dose- and time-dependent manner.CONCLUSION: TFBF obviously inhibited the formation of AGEs of proteins in vivo and in vitro.

Aim To explore the vasodilative effect on rat thoracic aortic ring of total flavonoids of Buckwheat flowers and leaves(TFBFL) and the underlying mechanisms.Methods Isometric tension measurements were used to study the effect of TFBFL on isolated rat thoracic aorta rings.Laser scanning confocal microscope was employed to measure the concentration of intracellular free calciums.Results In aorta rings precontracted with phenylephrine or potassium chloride,TFBFL caused a dose-dependent relaxation in both endothelium-intact and denuded rings and the relaxant effect of TFBFL was more potent on endothelium-intact aorta rings than that on endotheliumdenuded aorta rings(P

Aim To investigate the influence of total fl avones of buckwheat flower (TFBF) on the productivity of the non-enzymatic advanced glycation end products (AGEs) in vivoand vitro. Methods TFBF in different dosages (0.1 g?kg -1?d -1,0.2 g?kg -1?d -1,0.4 g?kg -1?d -1) was taken orally by streptozotocin-induced diabetic rats for 12 wk. After the treatment, blood glucose, fructosamine and AGEs in plasma and kidney were measured. Meanwhile, glucose and bovine serum albumin (BSA) were incubated with TFBF at different concentrations (0.01 mg?L -1,0.05 mg?L -1,0.10 mg?L -1) respectively for 4,8,12 wk.The fluorescence intensity of glycated BSA was detected by a spectrophotometer BSA was detected spectrophotometer.Results TFBF significantly lowered the level of blood glucose in diabetic rats (P

Objective:To observe the inhibitory effect on ?-glucosidase of 10 kinds Chinese herbs and to screen the Chinese herbal medicines which have great inhibitory effect on ?-glycosidase.Methods:The ?-glucosidase was extracted from small intestine of rat.The amount of glucose was measured with produced from substrate of malt sugar.The inhibitory effect of 10 kinds of Chinese herbs on ?-glucosidase was observed by this enzyme reaction system.Then disposable gastric perfused malt sugar(2 g/kg) and the extraction screened at the same time,detected the levels of blood glucose after 60 min.The positive control group is acarbose(ACAR) group.Results:The three kinds Chinese herbs(Chishao,Shanzhuyu and Sangbaipi) showed very good inhibitory activities,and they showed obviously concentration-effect curve relationship.Among them,the inhibitary activity of Sangbaipi is stronger than Chishao and Shanzhuyu.While the dose of Sangbaipi reached 10mg/mL,the inhibition rate arrived 80%,which effect was equivalet to the dose of 1mg/ml acarbose.The results of postprandial blood glucose in vitro showed us:Sangbaipi,Chishao and Shanzhuyu can inhibit postprandial blood glucose levels in rats that have been disposable gastric perfused malt sugar after 60min(P0.05).Conclusion:The three kinds of Chinese herbs(Chishao,Shanzhuyu and Sangbaipi) can inhibit ?-glucosidase activity obviously in both vitro and vivo.

OBJECTIVETo explore the effect and mechanism of flavones of buckwheat flower and leaf (FBFL) on lowering blood glucose and improving insulin resistance in type 2 diabetic rats.

METHODSeventy healthy male Wistar rats were used in this trial. Ten of them were selected randomly as normal group; the others were given fat milk by intragastric administration daily, from the 14th day on, low dose tetraoxypyrimidine was added by intraperitoneal injection every other day for three times. Rats with fasting (72 hours after the last injection) blood sugar > or = 16.7 mmol x L(-1) and K(IPT) < 60% of normal group were selected as type 2 diabetic model with insulin resistance, which were randomly divided into 5 groups: model group. LGLT group; low, moderate and high dosage FBFL groups (L-FBFL; M-FBFL; H-FBFL). Every rat was treated accordingly for 4 weeks; then FBG, FFA, INS were detected and ISI was calculated to evaluate the degree of insulin resistance. Liver PTP1B expression was determined by immunohistochemistry method. staining were observed by light microscopy.

RESULTFBFL could dose-dependently inhibit the rising of FBG, FFA, INS, improve the state of insulin resistance and reduce the expression level of liver PTP1B.

CONCLUSIONFBFL could effectively improve insulin resistance in type 2 diabetic rats induced by tetraoxypyrimidine and fat milk and showed dose-dependence relationship.

Animals ; Diabetes Mellitus, Type 2 ; drug therapy ; genetics ; metabolism ; Disease Models, Animal ; Fagopyrum ; chemistry ; Flavones ; administration & dosage ; Flowers ; chemistry ; Gene Expression ; drug effects ; Humans ; Insulin Resistance ; Liver ; drug effects ; metabolism ; Male ; Plant Extracts ; administration & dosage ; Plant Leaves ; chemistry ; Protein Tyrosine Phosphatase, Non-Receptor Type 1 ; genetics ; metabolism ; Random Allocation ; Rats ; Rats, Wistar