ABSTRACT
ObjectiveTo observe the effects of the water extracts of Trichosanthis Radix-Polygonati Rhizoma at different ratios on glucose and lipid metabolism in KKAy mice with spontaneous type 2 diabetes and explore the mechanism of the extract in alleviating insulin resistance based on phosphatidylinositol 3-kinase （PI3K）/protein kinase B （Akt）/forkhead box O1 （FoxO1） signaling pathway. MethodThe 8-week-old C57BL/6J male mice were taken as the normal control group， and KKAy male mice of the same age were randomly assigned into a model group， a metformin group， Trichosanthis Radix-Polygonati Rhizoma groups at the ratios of 1∶1 （Trichosanthis Radix 30 g， Polygonati Rhizoma 30 g）， 1∶3 （Trichosanthis Radix 15 g， Polygonati Rhizoma 45 g）， and 1∶5 （Trichosanthis Radix 10 g， Polygonati Rhizoma 50 g） according to blood glucose level and body weight， with 6 mice in each group. The administration lasted for 8 weeks， and the body weight （BW） and fasting blood glucose （FBG） of mice were recorded at the same time points of the 2nd， 4th， 6th， and 8th weeks， respectively. Oral glucose tolerance test （OGTT） was performed at the 7th week. After drug administration， the serum levels of total cholesterol （TC）， triglyceride （TG）， low-density lipoprotein cholesterol （LDL-C）， high-density lipoprotein cholesterol （HDL-C）， and fasting insulin （FINS） were measured， and homeostasis model assessment-insulin resistance （HOMA-IR） index was calculated. The liver tissue samples were stained with hematylin-eosin （HE） and periodic acid-Schiff （PAS） for observation of the fat distribution and glycogen content. The protein levels of PI3K， Akt， p-Akt， FoxO1， and p-FoxO1 in the liver were determined by Western blot. ResultCompared with the normal group， the model group showed increased food intake， FBG， glucose tolerance， FINS， HOMA-IR， TC， TG， and LDL-C （P<0.01）， and down-regulated protein levels of PI3K， Akt， phosphorylaison （p）-Akt， FoxO1， and p-FoxO1 in the liver （P<0.01）. Compared with the model group， Trichosanthis Radix-Polygonati Rhizoma lowered FBG and HOMA-IR （P<0.05， P<0.01）. In particular， the combination at the ratio of 1∶3 showed the best performance （P<0.01） comparable to metformin. Furthermore， Trichosanthis Radix-Polygonati Rhizoma at different ratios lowered blood glucose at different time points of OGTT （P<0.05） and TC and LDL-C （P<0.01）. Additionally， the combination at the ratio of 1∶3 reduced TG （P<0.01）. The liver of mice in the drug administration groups showed regular morphology， with few lipid droplets and rich glycogen. Western blot showed that Trichosanthis Radix-Polygonati Rhizoma up-regulated the protein levels of PI3K and p-Akt， down-regulated the protein level of FoxO1， and up-regulated the protein level of p-FoxO1 （P<0.05）. ConclusionTrichosanthis Radix-Polygonati Rhizoma， especially at the ratio of 1∶3， lowered the FBG， TC， LDL-C， and HOMA-IR index， promoted liver glycogen synthesis， and reduced steatosis in KKAy mice， which may be related to the regulation of PI3K/Akt/FoxO1 signaling pathway in the liver.