Effect of Modified Gegen Qinliantang on TGR5/cAMP/GLP-1 Signaling Pathway in Pancreatic Tissue of Type 2 Diabetes Mellitus db/db Mice / 中国实验方剂学杂志

ABSTRACT

ObjectiveTo discuss the effect of modified Gegen Qinliantang （MGQT） on blood glucose and lipids and Takeda G protein-coupled receptor 5 （TGR5）-related pathways in pancreatic tissue of obese type 2 diabetes mellitus （T2DM） mice. MethodA total of 10 male specific pathogen free （SPF） m/m mice （7 weeks old） and 50 male SPF （7 weeks old） were adaptively fed for one week in SPF laboratory. The m/m mice were included in the blank group. T2DM was induce d in the 50 db/db mice. The model mice were randomized into the model group， metformin group （0.2 g·kg-1）， high-dose， medium-dose， and low-dose （31.9， 19.1， 6.4 g·kg-1） MGQT groups， with 10 in each group， and the drug dose was10 mL·kg-1. The model group and the blank group received distilled water of the same volume. The administration lasted 12 weeks （once/day）. Fasting blood glucose （FBG） was detected regularly. After 12 weeks of administration， serum levels of glycated serum protein （GSP）， serum glucose （GLU）， total cholesterol （TC）， triglycerides （TG）， high-density lipoprotein cholesterol （HDL-C）， and low-density lipoprotein cholesterol （LDL-C） were detected. Pathological changes in the pancreatic tissue were based on hematoxylin-eosin （HE） staining. Western blot was used to determine the protein expression of TGR5， protein kinase A （PKA）， phosphorylated （p）-PKA， cyclic-AMP response element binding protein （CREB）， p-CREB， proprotein convertase 1/3 （PC1/3）， and glucagon-like peptide-1 （GLP-1） in pancreatic tissues. The level of cyclic adenosine monophosphate （cAMP） in pancreatic tissue was determined by enzyme-linked immunosorbent assay （ELISA）. ResultCompared with the blank group， the model group had pathological changes in pancreatic tissue， high levels of FBG， GSP， GLU， TC， TG， and LDL-C （P<0.01）， low level of HDL-C （P<0.05）， low protein expression of TGR5， p-PKA （Thr197）/PKA， p-CREB （Ser133）/CREB， PC1/3， and GLP-1 in pancreatic tissue （P<0.01）， and low content of cAMP in the pancreas （P<0.01）. Pancreatic tissue lesion in the treatment groups were milder than that in the model group. Both the high-dose MGQT and metformin can reduce the levels of FBG， GSP， GLU， TC， TG， and LDL-C in db/db mice （P<0.05， P<0.01） and increase the level of HDL-C （P<0.01）. Except the GLP-1 protein in the medium-dose MGQT group， the protein expression of TGR5， p-PKA （Thr197）/PKA， p-CREB （Ser133）/CREB， PC1/3， and GLP-1 in the high-dose and medium-dose MGQT groups and the metformin group increased compared with that in the model group （P<0.05， P<0.01）. The content of cAMP in the pancreatic tissue of the high-dose and medium-dose MGQT groups and the metformin group was raised compared with that in model group （P<0.05， P<0.01）. ConclusionMGQT can improve the glucose homeostasis in db/db mice with T2DM by regulating TGR5/cAMP/GLP-1 signaling pathway-related protein expression.