AIM: To investigate the effects of
glycyrrhiza on impaired glucose tolerance (IGT) induced by D-galactose (D-gal) in rats,
analyze the sex differences and compare with
metformin and silibinin.METHODS: The experiment was conducted at the Common Animal Laboratory, Department of Pharmacology, Guangzhou Institute of Traditional Chinese Medicine and Materia Medica.①Totally 103 SD rats of 6-8 weeks old and either sex were randomly divided into 5 groups: control group (n=21), model group (n=18), glycyrrhizia group (n=22), metformin group (n=20) and silibinin group (n=22). The solvent of same dose was injected intraperitoneally continuously for 56 hours in the control group while 150 mg/kg D-gal was given intraperitoneally in other groups, once a day continuously for 56 days to establish the IGT models. From the 14th day of model establishment, 0.44 g/kg glycyrrhizia suspension (main component: glycyrrhizia, produced by Guangdong Yifang Pharmaceutical Company, batch number:020315, 5 g/pocket, suspension was obtained by the distilled water mixing glycyrrhizia granules) was administrated intragastricallly in the glycyrrhizia group, while 0.25 g/kg silibinin solution (produced by Jiangsu Zhongxing Pharmacy Company Limited, number: 20030303, 50 mg/sheet) and 0.25 g/kg metformin solution (produced by Shenzhen Zhonglian Pharmaceutical Company, batch number: 200212305, 0.5 g/sheet) were given intragastrically in the silibinin group and the metformin group, respectively. The three kinds of solutions were given once a day continuously for 42 days.②After the model establishment, the body mass of rats was weighed. The fasting blood glucose (FBG) and 2-hours blood glucose (2hBG) after oral glucose tolerance test (OGTT) were detected and the different value was compared.③The measurement data were compared with t test (The t'test was used for variance nonhomogeneity).RESULTS:Totally 103 rats were involved in the result analysis.①FBG in the groups of control,
glycyrrhiza, metformin and silibinin were similar with that in the model group (P > 0.05), while the content of 2hBG after OGTT was significantly higher in model group than in groups of control, glycyrrhiza, metformin and silibinin (t=6.521 4, t=3.586-5.980,P < 0.01), which showed the insulin resistance for IGT. The difference between FBG and 2hBG after OGTT was lower in the groups of glycyrrhiza, metformin and silibinin than in the model group(t=2.897-6.094,P < 0.01),which indicated the improvement in D-gal-induced IGT. Moreover, the body mass of rats in model group was similar with that in groups of glycyrrhiza, metformin and silibinin, and lower than that of control group, with the insignificant difference (P > 0.05). So did the difference between groups in male rats.②FBG and 2hBG after OGTT of female rats in the model group were significantly higher than that in the control group (t=3.401,6.858,P < 0.01), which showed the insulin resistance for IGT. The FBG of female rats in glycyrrhiza and metformin groups were significantly lower than that in the model group (t=2.288,2.301,P < 0.05) while the FBG in silibinin group was not different from that in model group (P > 0.05) 2hBG after OGTT of female rats of three medication groups were significantly lower than that in the model group, and the difference between FBG and 2hBG after OGTT of female rats in three medication groups were significantly lower than that in the model group (t=4.176 3-6.371 6,P < 0.01), which indicated the improvement of IGT. The body mass of male rats in the medication groups was not different from those in control group and model group (P > 0.05).CONCLUSION: ①D-gal can induce the insulin resistance expressed as IGT, particularly in the female rats.②The glycyrrhizin, metformin and silibinin can antagonize D-gal-induced insulin resistance and improve IGT.