The Effects Of Two Typical Honeys On Glucose And Lipid Metabolism In Diabetic Mice And The Mechanism

Diabetes mellitus is a metabolic disease characterized by hyperglycemia,which is mainly caused by insulin resistance or insufficient insulin secretion.The population of diabetes is on the rise in recent years,and China has the largest number of diabetes in the world.It is extremely urgent to find the intervention and prevention of this disease.The intake of sweetener is a problem which can not be neglected in the intervention of diabetes.Honey is used both as natural sweetener and medicine,which comprised of predominantly fructose and glucose,as well as other bioactive constituents and microconstituents such as vitamins,minerals,acids,enzymes and polyphenols.Related research showed that,honey had lower glycemic index than glucose and sucrose,and also have the antioxidative,anti-inflammatory and anti-lipid peroxidative activities.Although there are some animal and clinical experiment shows that honey could reduce blood glucose and act as an antidiabetic agent,the lack of diverse origin honey samples in antidiabetic test showed limitations in this research.It’s difficult to value the influence of diverse origin and different dose of honey on DM and the molecular mechanism behind the hypoglycemic of honey is still unknown.Our research chooses two kinds of typical honey in China,the low fructose/glucose rape honey and the high phenolic compounds buckwheat honey,as the test subject.A type 2 diabetic mellitus（T2DM）model in male KM mice was developed for this experiment.After determining the components of two honeys,the influences of postprandial blood glucose fluctuation,the inhibition ofα-glucosidase,the intervention effects on T2DM and the mechanism in glucose metabolism has been studied.The main contents are as follows:（1）The major carbohydrate component in buckwheat honey and rape honey was fructose and glucose,maltose was not detected.The major carbohydrate component in buckwheat honey was fructose 32.33±1.37%,glucose 33.13±2.12%and sucrose0.91±0.09%.The major carbohydrate component in rape honey was fructose32.03±0.44%,glucose 43.90±1.37%.Maltose was not detected in both two honeys.The top three macroelement of 2 honeys was potassium,phosphorus and calcium.Total phenolics and total flavonoids of buckwheat honey was 1370.31±59.65 mg/kg and total flavonoids 47.85±0.46 mg/kg.Total phenolics and total flavonoids of rape honey was1370.31±59.65 mg/kg and total flavonoids 47.85±0.46 mg/kg.Macroporous resin XAD-2was adopted to adsorb the phenolic compounds of honey,then the composition of quantitative analysis was identified by HPLC.7 phenolic acids and 4 flavonoid was detected in buckwheat honey extracts,the three highest components were p-hydroxybenzoic acid,chlorogenic acid and pcoumaric acid.6 phenolic acids and 6flavonoid was detected in rape honey extracts,the three highest components were benzoic acid,kaempferol and quercetin.（2）Establishing type 2 diabetic mellitus（T2DM）model in male KM mice with different doses of streptozotocin（STZ）（50,60,70,80 mg/kg.b.w）and high-carbohydrate-fat diet fed for 4 weeks.It was found that each group with intraperitoneal injection of STZ（50,60,70,80 mg/kg.b.w）were diagnosed diabetes mellitus at 28^th,14^th,7^th and 7^th day separately after intraperitoneal injection with STZ for3 days.After the STZ injection had been finished for 5 weeks,the blood glucose,oral glucose tolerance test,blood lipid,liver injury,kidney injury in all groups were tested.The mice in four diabetes mellitus groups showed fibrosis,atrophy and vacuolization in the islets with different severities of nonalcoholic fatty liver and minor glomerular abnormalities.The disorder of lipid metabolism and the degree of damage to liver,kidney and islet cell was varied with the dosage of STZ.It found that type 2 diabetes mellitus model can be successfully developed with no mortality by high fat diet feeding for 4weeks with 70 mg/kg.b.w STZ intraperitoneal injection for 3 days induce.This model has the similar biochemical and pathological changes to human T2DM with nonalcoholic fatty liver disease and diabetic nephropathy.（3）T2DM mice model was established and the postprandial glucose was tested while different dose of honey and honey analogue were administrated to healthy and T2DM mice.The inhibition activity and inhibitory kinetics onα-glucosidase of buckwheat honey extraction and rape honey extraction were studied to evaluate the mechanism of decrease of the postprandial glucose level.The results showed that the influences on postprandial glucose level of the same dose of buckwheat honey and rape honey had no significant difference.Oral administration of rape honey and buckwheat honey in 1.0 g/kg.b.w could not lead to a significant increase in glucose levels in normal and T2DM mice whereas the honey analogue significantly raised the blood glucose levels in normal and T2DM mice even at this low dosage.In vitro antidiabetic activity experiments,buckwheat honey polyphenol extraction and rape honey polyphenol extraction was found to show a inhibition activity onα-glucosidase in a mixed-type manner.The affinity of these inhibitors for free enzyme is graeter than that with enzyme-substrate complex.（4）T2DM mice model was established and buckwheat honey,buckwheat honey with metformin,rape honey,rape honey with metformin were administrated to T2DM mice for5 weeks.Diet intake,water intake,body weight,blood lipids,liver injury,kidney injury and oxidative stress-mediated injury were measured to study the intervention effect of honey and honey with metformin on T2DM.The result showed that honey and honey with metformin could decrease the fasting blood glucose,oral glucose tolerance,insulin resistance,glycosylated hemoglobin and glycated serum protein.It could also alleviate the symptom concludes excessive drink,excessive food,diuresis and body thin.Compared with T2DM control group,the alanine aminotransferase（ALT）,aspertate aminotransferase（AST）,blood urea nitrogen（BUN）,creatinine（CRE）and malonaldehyde（MDA）in serum were significantly decreased in all treated group,superoxide dismutase（SOD）in serum was significantly increased in all treated group.Pathological analysis also found improved liver tissue injury and kidney tissue injury in four honey treated groups.For blood lipid levels,rape honey and rape honey with metformin could significantly decrease the serum total cholesterol（TC）,the ratio of LDL-C/TC,Atherogenic Index and Cardiovascular Risk Index.In the regulation of the key enzymes in glucose metabolism,intake both buckwheat honey and rape honey could significantly increase the activity of glucokinase in liver and significantly decrease the activity of glucose-6-phosphatase,phosphoenolpyruvate carboxykinase,pyruvate carboxylase and pyruvate dehydrogenase kinase in liver.These findings provide insight into the mechanism behind the hypoglycemic of honey and showed influences on three metabolic pathways:Motivating the activity of enzyme in glycolysis to accelerate the catabolism of glucose;Inhibiting the activity of enzyme in gluconeogenesis to reduce the glucose production;Inhibiting the activity of enzyme in pyruvate metabolism to accelerate the aerobic oxidation of pyruvate.In conclusion,rape honey and buckwheat honey could optimize the symptom of hyperglycemia and dyslipidemia,and had a significant protective effect on liver injury and kidney damage in T2DM mice.The molecular mechanisms behind the hypoglycemic effect of honey were the regulation of key enzyme in glucose metabolism.This study proved a hypoglycemic function of honey and evaluated the dosage effect on T2DM mice.It provides a theory foundation for a suitable intake of honey by T2DM patients.