Protective Effects Of Ginkgo Biloba Extract On Apoptosis Of Pancreatic β-cells In Insulin Resistance Rats Induced By High Fatty Diet

The diabetic incidence is rising rapidly nowadays and diabetes mellitus has become the third largest disease only behind of the cardiovascular diseases and cancer which significantly harm to human health. Insulin resistance is an important pathogenesis of cardio-cerebral vascular diseases and diabetes mellitus, and has close relationship to their occurrence and development. The treatment against pathophysiological mechanisms of diabetes mellitus and cardio-cerebral-vascular disease is of great significance. With the development and application of anti-diabetic drugs, such as insulin, insulin secreting drugs, insulin sensitizing agents, we have more choices for the treatment of diabetes mellitus.Despite the constant progress made in the treatment of diabetes mellitus, now, there still lacks of effective means to control diabetes mellitus and the complications in advance. To prevent diabetes mellitus and eliminate its hazards fundamentally has become an important question concerned by many people. But the prevention process faces varying problems, such as poor compliance of patients, drug toxicity, high price, and so on. To find a more effective and economic drug while has less adverse reactions has become a hot topic in the intervention of insulin resistance in diabetes mellitus.Ginkgo biloba extract is used mainly on the treatment of cardiovascular diseases and cerebral-vascular diseases. We have not seen any research reports about the protective effect of Ginkgo biloba extract on the pancreaticβ-cells of insulin resistance rats. Therefore, we investigate the protective effects of Ginkgo biloba extract on the apoptosis of pancreaticβ-cell in insulin resistance rats with immunohistochemistry, flow cytometry techniques.Objective: We determine the blood lipid, serum free fatty acid, the apoptotic level of pancreaticβ–cell and apoptosis-related factors in insulin resistant rats induced by high fatty diet. Rosiglitazone is served as a control drug. Preliminarily we research the protective effect of ginkgo biloba extract on improving insulin sensitivity and inhibiting pancreaticβ-cells apoptosis. This topic will provide theoretical and experimental evidence about the protective mechanism of Ginkgo biloba extract on diabetes mellitus.Methods:①40 adult, healthy, clean, male Wistar rats, were randomly divided into two groups taking either normal chow (NC group, n=10)or high fat diet(HF group ,n=30) respectively. Four weeks later, insulin resistance model was successfully duplicated, HL rats were randomly divided into hyperlipidemia group(HL,n=10), Rosiglitazone group(HL+ HL+RSG,n=10), Ginkgo biloba extract group (HL+EGb, n=10). ②Body weight (BW), serum triglyceride (TG), serum total cholesterol (TC), serum free fatty acid (FFA), fasting plasma glucose (FPG), fasting serum insulin(FINS) were determined every 4 weeks during the 8-week feeding. IR was evaluated by Insulin sensitivity index (ISI) and insulin resistance index(HOMA-IR) from FPG and FINS.③Observing the apoptotic rate of pancreaticβ-cells with methods of flow cytometry(FCM) and terminal deoxynucleotidyl transferase (TdT) dUTP nick end labeling(TUNEL) .Result: 1. The HL group showed hypercholesteremia, hyperglycemia, hyperinsulinemia, hypertriglyceridemia and the level of Free Fatty Acid increased, the insulin sensitivity index (ISI) decreased while the HOMA insulin resistance index (HOMA-IR) increased compared to the NC group, and insulin resistance was induced in this way. While body weight gained slightly in HL group, there was no significant difference among the four groups(p >0.05).2. 8 weeks later, the fasting blood glucose (FBG), fasting insulin(FINS), the HOMA insulin resistance index (HOMA-IR) , serum triglyceride (TG), serum total cholesterol (TC), serum free fatty acid (FFA)of the HL group were significantly increased, the insulin index (ISI) significantly decreased compared with the NC group(p <0.05). Compared with the HL group, fasting blood glucose (FBG), fasting insulin (FINS), the HOMA insulin resistance index(HOMA-IR), serum triglyceride (TG), serum total cholesterol (TC), serum free fatty acid (FFA) of the HL+EGb group, were significantly decreased and the insulin index (ISI) significantly increased(p <0.05). There was no significant difference between the HL+EGb group and the HL+RSG group.3. Compared with the NC group, the apoptotic rate of pancreaticβ-cell step up significantly in HL group(p <0.05); the apoptotic rate of pancreaticβ-cell in HL+EGb group and HL+RSG group descended significantly 8 weeks later. But there were no statistical difference between the two treating groups(p >0.05).4. Compared with the NC group, the bcl-2 protein expression level of pancreaticβ-cell decreased significantly in HL group, the bax protein expression level of pancreaticβ-cell increased significantly(p <0.05); Compared with the HL group, the bcl-2 protein expression level of pancreaticβ-cell is increased significantly and the bax protein expression level of pancreaticβ-cell is descended significantly in the two treating groups(p <0.05); but there was no statistical difference between the two treating groups(p>0.05).5. The TUNEL index and the apoptotic rate were negatively correlated with fasting blood glucose (FBG), fasting insulin (FINS), serum triglyceride (TG), serum total cholesterol (TC), serum free fatty acid (FFA), the expression level of bax protein was positively correlated with the expression level of bcl-2 protein.Conclusion: 1. The HL group showed hypercholesteremia, hyperglycemia, hyperinsulinemia, hypertriglyceridemia and High-Free Fatty Acid (FFA) Level by high fat-feeding, the insulin resistance index (ISI) decreased while the HOMA insulin resistance index (HOMA-IR) increased compared to the normal group, insulin resistance was induced in this way.2. Ginkgo biloba extract could decrease serum triglyceride (TG), serum total cholesterol (TC), serum free fatty acid (FFA), fasting blood glucose (FBG), fasting insulin (FINS), the HOMA insulin resistance index (HOMA-IR) and improve insulin sensitivity index (ISI), the effect on improving insulin resistance is similar with Rosiglitazone.3.Ginkgobiloba extract could significantly protect apoptosis of pancreaticβ-cell, and change the expression of apoptosis-related proteins. For example, it increased the expression of bcl-2 protein which inhibiting apoptosis, at the same time, it decreased the expression of bax protein which promoting apoptosis.4. In analysis of correlation, the TUNEL index and the apoptotic rate was negatively correlated with fasting blood glucose (FBG), fasting insulin (FINS), serum triglyceride (TG), and serum total cholesterol (TC), serum free fatty acid (FFA), the expression level of bax protein and positively correlated with the expressional levels of bcl-2 protein. These results suggested that the effect of Ginkgo biloba extract on protecting the pancreaticβ-cells was closely related to the expression levels of apoptosis-related protein and blood lipid.