The Effect Of Gynostemma Pentaphyllum Seed Oil On Glucose And Lipid Metabolism And Its Mechanism

Diabetes mellitus is a chronic disease that seriously threatens human health.The cause of the disease is complicated.90%to 95%of diabetes mellitus is type 2 diabetes.Its main feature is hyperglycemia caused by insulin resistance,and is often accompanied by diseases such as hypertension,hyperlipidemia,atherosclerosis,and polycystic ovary.At present,there are many kinds of drugs for diabetes,such as metformin,in clinical practice,but the long-term use of these drugs will produce toxic and side effects.Literature searches indicate that Chinese herbal extracts have a prominent role in the treatment of chronic diseases such as diabetes.Gynostemma pentaphyllum seed oil is a functional oil rich in conjugated linolenic acid extracted from the seeds of G.pentaphyllum.Conjugated linolenic acid has anti-atherosclerosis,anti-tumor,anti-inflammatory and lipid-regulating functions.In this thesis,the effects and possible mechanisms of G.pentaphyllum seed oil and its main constituent,G.pentaphyllum seed fatty acids,on the metabolism of glucose and lipid in insulin-resistant mice and cells were investigated in vitro and in vivo.The main experimental methods and results are as follows:1.Establishment and evaluation of insulin resistance mouse modelMale Kunming mice were used to establish an insulin resistance model.Mice were modeled by intraperitoneal injection of 40 mg kg^-1 of streptozotocin combined with high-fat diet,and fasting blood glucose≥7.8 mmol L^-1 was confirmed as model success.After successful modeling,different drugs were used for gavage treatment.The stability of the model and the efficacy of the drug were determined by body weight and fasting blood glucose after gavage treatment.It was found that the G.pentaphyllum seed oil treatment group can significantly improve the body weight and fasting blood glucose in insulin resistant mice.The oral glucose tolerance and area under the curve also demonstrated that G.pentaphyllum seed oil significantly improved oral glucose tolerance in insulin resistant mice.At the same time,liver H&E staining and serum levels of aspartate aminotransferase,alanine aminotransferase,urea nitrogen,and creatinine showed that G.pentaphyllum seed oil could improve liver and kidney damage caused by high-fat feeding and streptozotocin injection.2.Effect of G.pentaphyllum seed oil on insulin resistance lipid metabolismThe detection of four lipid levels（total cholesterol,triglyceride,high-density lipoprotein,and low-density lipoprotein）demonstrated that G.pentaphyllum seed oil can lower total cholesterol,triglyceride,and low-density lipoprotein and increase high-density lipoprotein.The hormone level test showed that G.pentaphyllum seed oil can increase serum hormones such as serum insulin,adiponectin,and leptin.G.pentaphyllum seed oil can also reduce serum free fatty acid levels and improve insulin resistance.The composition of total fatty acids in the liver was detected by gas chromatography mass spectrometry.G.pentaphyllum seed oil can increase the levels of beneficial fatty acid n-3 fatty acids;detection of liver and skeletal muscle glucose transporter 4 protein expression by Western blotting indicated that G.pentaphyllum seed oil can increase glucose transporter 4 expression.3.Establishment and identification of HepG2 insulin resistance cell modelExogenous insulin was used to induce insulin resistance in hepatoma HepG2 cells.The determination of glucose uptake by cells was used to confirm whether the model was successfully established.It was found that insulin concentration of 10^-7 mol L^-1 induced insulin resistance for 24 h and could maintain 48 h.Therefore,it is reasonable to conduct drug screening and treatment within 48 hours.4.Effects of G.pentaphyllum seed fatty acids on glucose and lipid metabolism in insulin resistant HepG2 cellsThe concentration of the drug that did not kill insulin resistant HepG2 cells and was able to improve the glucose uptake of insulin resistant HepG2 cells was determined by MTT and glucose content assays.The detection of total cholesterol and triglyceride showed that the seed fatty acids of G.pentaphyllum could reduce the content of total cholesterol and triglyceride in insulin resistance HepG2 cells.Oil red O staining showed that the seed fatty acids of G.pentaphyllum decreased the lipid droplet level of insulin resistant HepG2 cells.Gas chromatography-mass spectrometry（GC-MS）was used to determine the total fatty acid composition of the cells.G.pentaphyllum seed fatty acids were found to increase the levels of n-3 fatty acids in the cells.G.pentaphyllum seed fatty acids were found to decrease the expression of acetyl-CoA carboxylase and increase fatty acid synthase by enzyme-linked immunosorbent assay.