Effect of Tangbikang Granules on PI3K Pathway in Type 2 Diabetic Mellitus Rats with Non-alcoholic Fatty Liver Disease / 中国实验方剂学杂志

ABSTRACT

ObjectiveThis study aims to investigate the therapeutic effect of Tangbikang granules（TBK） on type 2 diabetes mellitus （T2DM） complicated with non-alcoholic fatty liver disease （NAFLD） and to elucidate the underlying mechanism. MethodT2DM and NAFLD were induced in ZDF rats， which were then respectively treated （ig） with low-dose （0.625 g·kg-1）， medium-dose （1.25 g·kg-1）， and high-dose （2.5 g·kg-1） TBK for 12 weeks. Fasting blood glucose （FBG） and body mass were recorded every 4 weeks during the treatment. One week before sampling， the feed intake of rats was detected， and after 12 h night fasting， oral glucose tolerance test （OGTT） was performed. The area under the curve （AUC） was used to evaluate glucose tolerance， and the homeostatic model assessment for insulin resistance （HOMA-IR） was calculated. Blood in abdominal aorta and liver were collected for determination of blood glucose and lipid metabolism indexes： Fasting serum insulin （FINS）， serum total cholesterol （TC）， triglyceride （TG）， low density lipoprotein cholesterol （LDL-C）， high density lipoprotein cholesterol （HDL-C）， and nonesterified fatty acids （NEFA）. The liver was weighed to calculate the liver index， and the liver tissue morphology was observed and analyzed based on hematoxylin-eosin （HE） staining and periodic acid-Schiff （PAS） staining. The protein levels of insulin receptor substrate （IRS）， phosphatidylinositol 3-kinase （PI3K）， protein kinase B （Akt） and phosphorylated IRS and Akt were detected by Western blotting. All data were analyzed by SPSS 20.0. ResultThe feed intake of the model group was higher than that in the normal group （P<0.01）， and the feed intake the administration groups was lower than that in the model group （P<0.05， P<0.01）. At the 8th and 12th week， the body mass in the model group was lower than that in the normal group （P<0.01）. Compared with the model group， TBK reduced FBG in a concentration-dependent manner. The blood glucose level in OGTT and AUC in the model group were higher/larger than those in the normal group （P<0.01）. The blood glucose value in OGTT was decreased in TBK groups and the metformin group compared with that in the model group， and AUC in the administration groups was significantly different from that in the model group （P<0.01）. The serum level of FINS and HOMA-IR in the model group were higher than those in the normal group （P<0.01）， and they were lower in the TBK groups than in the model group （P<0.01）. Serum levels of TG， TC， HDL-C， NEFA （P<0.05， P<0.01）， and LDL-C were higher in the model group than in the normal group. Serum levels of TG， TC， LDL-C， and NEFA in the TBK groups were lower than those in the model group， and the levels of TG， LDL-C， and NEFA in TBK groups were concentration-dependent （lowest levels in high-dose TBK group）. Compared with the model group， high-dose TBK significantly increased the level of HDL-C （P<0.05）. Liver index of the model group was higher than that in the normal group （P<0.01）. The liver index of the administration groups showed a decreasing trend with no significant difference from that in the model group. As for the HE staining result of liver， the model group had unclear structure of liver lobule， enlarged cells of different sizes， and obvious steatosis of hepatocytes. TBK of all doses alleviated liver injury， particularly the high dose. For the PAS staining， compared with the normal group， the model group demonstrated significant fat vacuoles and significant reduction in purplish red glycogen granules in the cytoplasm. The staining results of high- and medium-dose groups of TBK were more similar to the normal group. Western blot was used to detect the protein expression of liver tissue. The expression of PI3K protein， p-IRS1/IRS1， and p-Akt/Akt in the model group were lower than those in the normal group （P<0.01）， and they were higher in the high-dose TBK group than in the model group （P<0.01）. ConclusionTBK exerts therapeutic effect on T2DM combined with NAFLD in ZDF rats by activating the typical PI3K signaling pathway.