Protective Mechanism Of Resveratrol In Advanced Glycation End Products Induced Type 2 Diabetes Islet Injury

Objective: Diabetes mellitus,manifested as chronic hyperglycemia,is a complicated chronic metabolic disease affected by many factors.The continuous hyperglycemia is the most of the main reasons to aggravate diabetes and induce various complications.Advanced glycation end products(AGEs)are heterogeneous groups of stable irreversible compounds that result from the non enzymatic reaction between the reducing sugar and proteinor amino acid in the continuous hyperglycemia state.AGEs gradually accumulate in tissues and induced a series cascade of oxidative stress reactions,which play an important role during the process of diabetes mellitus and complications,such as diabetic nephropathy,atherosclerosis and diabetic retinopathy.Recent studies have shown that AGEs could cause ?-cell apoptosis directly,impair insulin synthesis and secretion.It is one of the major factors inducing and aggravating diabetes.Resveratrol(RSV),a polyphenolic compound,is an active ingredient in various plant extracts such as peanuts,grapes,knotweed and mulberry,which was first discovered in 1924.Studies have shown that RSV is a natural free radical scavenger and antioxidant,and it also play an important role in antidiabetes and reducing blood glucose.The mechanism was believed to be related to anti-oxidative stress,promoting insulin secretion and improving insulin sensitivity.However,it has rarely been reported that the protection of RSV reducing the formation of AGEs and oxidative stress on target organs.Therefore,based on previous studies,we explored the possible protective mechanisms of RSV on pancreatic islet injury induced by AGEs.In particular,we wanted to explore whether RSV could reduce the formation and accumulation of AGEs and play a protective role in the regulation of oxidative stress induced by AGEs in islet tissue.Methods: 1.Non-enzymatic glycation reaction system was established by using glyoxal-bovine serum albumin.Aminoguanidine was used as the positive control.RSV was used as the tested substance.Fluorescence value was used to judged the inhibition rate of AGEs production in vitro by colorimetric methed.2.Glycated serum(GS)was compound by D-glucosamine and fetal bovine serum at 37 °C for 3 weeks in the dark and it could mimics the AGEs formation in diabetic patients.INS-1 cells were used to establish the INS-1 cell AGEs injury model by using GS.We aimed to observe the protection effects of different doses of RSV on islet INS-1 cells damaged by AGEs and the antioxidative stress mechanism involved in it.3.The C57BL/6J mice were used to construct insulin-resistant type 2 diabetic model mice by 60% of high-fat diet and intraperitoneal injection of streptozotocin.Metformin treatment was used as positive control.RSV with different concentrations was used as tested substance.The mice were given RSV intragastric administration for 40 days.The improvements of diabetes-related biochemical indicators of type 2 diabetes mellitus mice in vivo experiments were studied,and the protective mechanism of RSV anti-oxidative stress was further explored.Result: 1.In vitro non-enzymatic glycosylation system,the inhibition rate of AGEs in the RSV(500 ?M)group gradually increased from the 5th day after this experiment.The inhibition rate was similar to aminoguanidine positive control group on the 11 th day.On the 23 rd day,the inhibition rate of AGEs in the RSV(500 ?M)group reached 86.23%,which significantly surpassed the aminoguanidine-positive control group.These results showed that RSV had a significant inhibitory effect on AGEs.2.In vitro cell experiments,we found that AGEs had obvious growth inhibitory effect on INS-1 cells and it could promote oxidative stress.RSV could significantly increase the proliferation rate of INS-1 cells and it significantly inhibited the AGEs-induced oxidative stress.It suggested that RSV had a significant protective effect on AGEs-induced INS-1 cell damage.RSV also enhanced the ability of clearing free radicals and the capacity of antioxidant in INS-1 cells.3.In vivo experiments,we found that RSV could effectively reduce blood glucose,improve glucose tolerance and insulin tolerance,reduce blood lipids,and reduce insulin resistance in diabetic mice.In addition,RSV could reduce the accumulation of AGEs in pancreatic tissue and reduce pancreatic tissue damage induced by AGEs and promote insulin secretion.RSV was effectively reducing oxidative stress in the islet of diabetic mice.Conclusions: 1.RSV could significantly inhibit the formation of AGEs,which might be an effective AGEs inhibitor in vitro;2.RSV had a significant protective effect on AGEs damaged INS-1 cell,and the mechanism might be closely related to improve the ability of antioxidative stress in INS-1 cells;3.RSV protected type 2 diabetes mice by reducing the accumulation of AGEs in pancreatic tissue,reducing oxidative stress,reducing pancreatic islet ?-cell damage,improving pancreatic islet secretory function.As a result,RSV improved glucose tolerance,insulin tolerance,insulin resistance and reduced blood sugar in type 2 diabetic mice.