| ObjectiveTo investigate the effects of Olive leaf extract on blood glucose metabolism,oxidative damage,glucose transporter 2 protein and gene expression in diabetic mice.This study provides a theoretical basis for the development and utilization of olive leaves.MethodsConstruction of a diabetic mouse model:Sixty SPF-grade ICR mice,male,weighing 20±2 g.Fifty mice were randomly selected as diabetic modules to feed high-sugar and high-fat diets.After 4 weeks,the mice were intraperitoneally injected with 0.5%streptozotocin 50 mg kg-1 for three consecutive days.Mice with a blood glucose level higher than 7.0 mmol/L for successful diabetes model.Animal experiment:A total of 40 diabetic model mice were selected and randomly divided into 4 groups according to the body weight of the mice.The group was the diabetic control group and the olive leaf extract low,medium and high dose groups.High-sugar and high-fat diets were fed during the experiment.Olive leaf extracts of 150 mg kg-1 ·d-1,500 mg kg-1·d-1 and 1000 mg kg-1·d-1 were administered intragastrically in the low，medium and high doses of olive leaf extract.The diabetic control group and the normal control group were given an equal volume of physiological saline once a day.The feeding was continuously administered for 3 weeks.The animals were sacrificed and samples of whole blood,spleen,liver and kidney were collected.Indicator determination:(1)Blood sugar metabolism:The fasting blood glucose level in the serum of each group of mice was determined by the glucose oxidase-peroxidase method.Serum glycated hemoglobin levels in each group of mice were determined by chemical colorimetry.To investigate the effects of olive leaf extract on blood glucose metabolism in diabetic mice;(2)Oxidative damage:The liver morphology of the mice in each group was observed by fixed,routine paraffin embedding,5μm section,hematoxylin-eosin staining and conventional light microscopy.The activity of serum glutathione peroxidase(GSH-PX)in each group of mice was determined by enzymatic reaction and color reaction.The activity of superoxide dismutase(SOD)in serum of each group was determined by xanthine oxidase method.Serum malondialdehyde(MDA)levels were determined in each group of mice using the thiobarbituric acid method.The effects of olive leaf extract on oxidative damage in diabetic mice were investigated by liver pathological observation and biochemical indicators;(3)Glucose transporter 2 expression:The expression level of glucose transporter 2 mRNA in the liver of diabetic mice was determined by RT-PCR;The expression level of glucose transporter 2 protein in the liver of diabetic mice was determined by Western Blot;The effects of olive leaf extract on the expression of hepatic glucose transporter 2 in diabetic mice were investigated by measuring the expression levels of glucose transporter 2 protein and mRNA.Result(1)Effects of olive leaf extract on blood glucose metabolism in diabetic mice:The blood glucose levels of the high,medium and low olive leaf extract dose groups were significantly lower than those of the diabetic model group.The glycated hemoglobin content of the high and medium olive leaf extract group was significantly lower than that of the diabetic model group,and the high dose group was significantly lower than the middle dose group.The above differences were statistically significant(P<0.05).(2)Effects of olive leaf extract on oxidative damage in diabetic mice:Compared with the diabetic model group,the liver cell line and hepatic sinusoids of the olive leaf extract and high dose group were arranged regularly,and the central vein structure was relatively complete.There was still a small amount of fat vacuoles in the liver tissue,and the interstitial hyperemia and inflammatory cell infiltration were significantly improved.The activity of Glutathione peroxidase in the high and medium olive leaf extract group was significantly lower than that in the diabetic model group,and the high dose group was significantly higher than the middle dose group.The superoxide dismutase activity of the high and medium olive leaf extract group was significantly lower than that of the diabetic model group,and the high dose group was significantly higher than the middle dose group.The levels of malondialdehyde in the high,medium and low olive leaf extract dose groups were significantly lower than those in the diabetic model group,and the MDA levels in the high dose group were significantly lower than those in the middle dose group.The above differences were statistically significant(P<0.05).(3)Effects of olive leaf extract on liver glucose transporter 2 in diabetic mice:The expression level of glucose transporter 2 mRNA in the high and medium olive leaf extract group was significantly higher than that in the diabetic model group,and the mRNA expression level in the high dose group was significantly higher than that in the middle dose group.The expression level of glucose transporter 2 protein in the high and medium olive leaf extract dose group was significantly higher than that in the diabetic model group,and the high dose group protein expression level was significantly higher than the middle dose group.The above differences were statistically significant(P<0.05).ConclusionOlive leaf extract reduced the blood sugar level and glycosylated hemoglobin content of diabetic mice,increased the activity of antioxidant enzymes,reduced the level of lipid peroxidation,improved the oxidative damage level of the body,increased the expression level of GLUT-2 protein and mRNA in liver and improved blood glucose metabolism disorders in diabetic mice. |
