RESUMEN
OBJECTIVE： To investigate the effects of total flavonoids from Psidium guajava leaves （GLTF） on the related factors for estrogen-associated receptor γ（ERRγ）/cyclic adenosine monophosphate responsive element binding protein H（CREBH）pathway in liver of type 2 diabetes mellitus（T2DM）model mice， and to investigate the specific mechanism of its hypoglycemic effect. METHODS： Healthy male ICR mice were collected. T2DM models were established by high-sugar and high-fat diet feeding combined with repeated intraperitoneal injection of low dose streptozotocin. According to the blood glucose value， model mice were randomly divided into model group， metformin group（positive control， 0.17 g/kg），Xiaoke jiangtang capsule group（positive control， 0.75 g/kg），GLTF low-dose and high-dose groups（0.047， 0.094 g/kg）， with 12 mice in each group. Another 12 normal mice were included in normal group. Except that normal group and model group were given constant volume of water intragastrically， other groups were given relevant solution 10 mL/kg intragastrically， qd， for consecutive 21 d. After administration， fasting blood glucose and serum insulin levels of mice were measured and insulin sensitivity index （ISI） was calculated. Histopathological changes of liver and pancreas were observed by HE staining. The protein expressions of ERRγ and CREBH in liver tissues were detected by immunoblotting. The mRNA expression of peroxisome proliferator-activated receptor-γ coactivator-1α（PGC1α）and CREB protein co-activator 2（TORC2）in liver tissue of mice were measured by RT-PCR. RESULTS： Compared with normal group， the levels of fasting blood glucose and serum insulin in T2DM mice were significantly increased in model group， while ISI was decreased significantly （P＜0.01）. The pathological changes of liver tissue were obvious and a large number of vacuoles could be seen. The number and volume of islets in pancreatic tissue decreased， and islet cells showed mild vacuolar lesions. The protein expression of ERRγ and CREBH， mRNA expression of PGC1α and TORC2 in liver tissue were increased significantly （P＜0.01）. Compared with model group， above blood glucose， insulin indexes and pathological changes were improved significantly in GLTF groups. Protein expression of ERRγ and CREBH， mRNA expression of PGC1α and TORC2 in liver tissue were decreased significantly （P＜0.05 or P＜0.01）. CONCLUSIONS： GLTF showed obvious hypoglycemic effect on T2DM model mice； its mechanism might be related to inhibiting ERRγ/CREBH signaling pathway.
RESUMEN
OBJECTIVE:To optimize the extraction technology of total flavonoids from Psidium guajava leaves and investigate the effects of total flavonoids from P guajava leaves on glucose tolerance in diabetic model mice.METHODS:Based on single factor test,using extraction time,solid-liquid ratio and the amount of ethanol as independent variables,comprehensive scores of the yield of hyperin,quercetin-3-O-β-D-arabinopyranoside,quercetin-3-O-α-L-furanarabino side ethyl acetate and extract as dependent variable,Box-Behnken design-response surface method was used to optimize the reflux extraction process of total flavonoids from P guajava leaves,and validation test was also conducted.Sixty mice were randomly divided into blank group,model group,metformin group (170 mg/kg),P.guajava leaves total flavonoids low-dose,medium-dose and high-dose groups (23.41,46.81,93.62 mg/kg,by the content of total flavonoids),with 10 mice in each group.Except for blank group,diabetic model was induced in those groups,and then model mice were given relevant medicine intragastrically once a day for consecutive 21 d,6 h after last medication given glucose 2.0 g/kg intragastrically.The levels of blood glucose were determined 0,0.5,1.0,2.0 h after intragastric administration of glucose,and the area under the curve (AUC) of blood glucose was calculated.RESULTS:The optimal technology of P guajava leaves total flavonoids was as follows as extracting twice,lasting for 1.0 h each time,solid-liquid ratio of 1 ∶ 17,ethanol volume fraction of 56％.In validation test,the contents of hyperin,quercetin-3-O-β-D-arabinopyranoside and quercetin-3-O-α-L-furanarabino side ethyl acetate were 2.57,3.38,2.26 mg/g(RSD＜2％,n=3);the yield of extract was 25.71％ (RSD=1.19％,n=3);average comprehensive score was 96.41 (RSD=l.34％,n=3);relative error was 3.57％ with the predicted value of 99.98.Compared with blank group,AUC of mice were increased significantly in each group;compared with model group,AUC of metformin group,P.guajava leaves total flavonoids medium-dose and high-dose groups were all decreased significantly,with statistical significance (P＜0.05 or P＜0.01).CONCLUSIONS:The optimal extraction technology is stable,feasible and controllable in quality.Total flavonoids from P.guajava leaves can promote the recovery to normal level of blood glucose.