Effects Of Baicalin On Glucolipid Metabolism And Its Mechanisms In Type 2 Diabetes

Backgrounds:Type 2 diabetes mellitus(T2DM)is a chronic metabolic disorder characterized by impaired homeostasis of glucose metabolism,which generally results from insulin resistance,or accompanied with relatively insufficient insulin secretion.And T2DM accounts for 90-95%of Diabetes mellitus patients.Baicalin as one of flavonoids compounds purified from the traditional medicine Scutellaria baicalensis Georgi,have broad potential prospects in type 2 diabetes and its complications treatment.Objective:To investigate the effect of glucolipid metabolism and its mechanisms in the period of development and progression of type 2 diabetes,we established the insulin resistance model,and insulin resistance accompanied with insulin deficiency model.And it is providing theoretical foundation and clinical development value in type 2 diabetes treatment.Methods:Male C57/B6J mice were randomly divided into two groups:normal control(ND)fed with normal diet and obesity fed with the high-fat diet(HFD).Both of the two T2DM models were successfully built,which were induced by high-fat diet and STZ.And then these modeling mice were divided into 4 groups according to blood glucose and their body weight.They are HFD,HFD+B,HFD+STZ,and HFD+STZ+B groups,and ten mice in each group.Two of the group mice were administrated with 200mg/kg baicalin,and the rest of control groups mice were oral administrated with equal amount of saline solution.After 16 weeks treatment of 200mg/kg/d baicalin,the mice were subjected for glucose and insulin tolerance test,and the level of triglyceride,total cholesterol,alanine transaminase,creatine kinase,and other related items in the serum isolated from the animals were determined by using automatic biochemical analyzer.The level of insulin and free fatty acid in the serum were examined using ELISA assay.Additionally,Lipid deposition was observed in the liver and skeletal muscle tissues isolated from the mice with H&E staining and/or Oil Red O staining.And pathological features in pancreas&islet were exhibited with H&E staining and immunohistochemical staining.The expression of AMPK,ACC,Akt and GSK-3β protein and their phosphorylated forms in liver and skeletal muscle were examined by Western blot assay.In vitro,the HepG2 cells were cultured in high glucose circumstance(25mM)to establish hepatic insulin resistance model.The expression of AMPK,ACC,Akt and GSK-3β protein and their phosphorylated forms were detected by Western blot assay to estimate the proper time point and concentration of baicalin.The antiproliferation and toxicity efficiency of baicalin on HepG2 cell was assessed with MTT assasy.In addition,the interaction between AMPK pathway and Akt/GSK3β insulin signaling pathway,and glucose consumption were examined and demonstrated using AMPK and Akt inhibitors or activators tests.Results:(1)Compared with the HFD and HFD+STZ group,baicalin 200mg/kg administrated for 16 weeks significantly decreased fasting blood glucose,fat ratio,liver coefficient,triglyceride,total cholesterol,low density lipoprotein,and body weight,impaired glucose and insulin tolerance in HFD and HFD+STZ group mice were also ameliorated greatly.Moreover,insulin levels in HFD mice serum was significantly decreased,while showed increasing evidently in HFD+STZ group mice with oral administration of 200mg/kg baicalin for 16 weeks.Therefore,baicalin has beneficial effects on hyperinsulinmia and insulin deficiency both in type 2 diabetes.(2)H&E staining and Oil Red O staining showed that lipid deposition and steatosis in liver and skeletal muscle tissues in HFD+STZ group were more serious than in HFD group.And baicalin(200 mg/kg/d)decreased lipid accumulation and improved the hepatic steatosis and lipid deposition induced by high fat diet or high fat diet combined STZ injections.Further study indicated that baicalin(200 mg/kg/d)in 16-week treatment improved the AMPK,ACC,Akt and GSK3βphosphorylation levels compared with HFD and HFD+STZ groups.Additionally,pancreas&islet were exhibited with H&E staining and immunohistochemical staining showed that baicalin ameliorated islets function and its pathological features,size and area.(3)The aspartate aminotransferase,alanine aminotransferase,creatine kinase,and urea nitrogen,and creatinine levels were decreased effectively with oral administration 200mg/kg/d baicalin for 16 weeks,demonstrating baicalin has low hepatic and renal toxicity and has tissue-protective effects.(4)In vitro,baicalin has non-cytotoxicity by MTT assay.And the optimal time and concentration of baicalin for high glucose induced HepG2 cells were 1h and 1μM.And in mechanisms of T2DM treatment of baicalin,PI3K/Akt pathway is necessary for baicalin-induced AMPK mediated GSK3β phosphorylation.And Akt/GSK3β also inhibited the AMPK signaling activity indirectly.Conclusion:Taken together,baicalin had great beneficial effects on glucose and lipid metabolism,as well as insulin level in T2DM mice induced by high fat diet and high fat diet combined with STZ injection And the mechanism was probably related to regulation of hepatic and skeletal muscle AMPK/ACC/Akt/GSK3β signaling pathway and the functional improvement of islets in T2DM mice.Understanding the comprehensive effects and mechanisms of baicalin on T2DM will provide new avenue for treatment of type 2 diabetes and other metabolic diseases.