Protective Effect And Mechanism Of Theaflavin Digallate On Vascular Endothelial Injury And Inflammatory Response Induced By High Glucose

Diabetes is a common chronic metabolic disorder.In recent decades,with the changes of living conditions and lifestyles of Chinese residents,the incidence of typeⅡdiabetes mellitus(T2DM)has been increasing,and the total number of patients has been increasing,showing a trend of younger age.T2DM can harm multiple tissues and organs in the whole body,leading to numerous complications,among which cardiovascular diseases are the most significant,seriously threatening the life and health of patients and reducing the quality of life of patients.The occurrence and development of T2DM and its cardiovascular complications are closely related to diet and nutrition,so it is of great significance to explore dietary approaches to prevent and treat T2DM and its cardiovascular complications.Black tea is a popular drink all over the world.Theaflavins are the main natural active ingredients in black tea.There are four main theaflavins in black tea:theaflavins(TF1),theaflavin-3-gallate(TF-3-G),theaflavin-3’-gallate(TF-3’-G)and theaflavin-3,3’-gallate(TFDG).Among them,TFDG has the highest content and the strongest activity.However,until now,there are few studies on the protective effect and mechanism of TFDG on cardiovascular injury in diabetes,and the specific effect and molecular mechanism are unclear.This topic using cell model in vitro and in vivo animal experiment model,to observe the evaluation TFDG the protective effect on diabetic vascular endothelial damage,especially in-depth study TFDG effects on vascular injury early inflammatory reaction and mechanism,to explore TFDG NRLP3 inflammatory pathways control effect,reveal TFDG molecules give play to the role of vascular endothelial injury protection mechanism.The purpose of this study is to explore new strategies for the early prevention and treatment of diabetic vascular injury,and to further reveal the biological effects and molecular mechanisms of black tea and theaflatins.The results of this study will have certain theoretical and practical significance for guiding the scientific diet and prevention and treatment of diabetic population.Part Ⅰ:Human umbilical vein endothelial cells(HUVECs)were cultured in vitro.The model group was treated with high glucose(33.0 mmol/L glucose)for 24 h to induce cell damage,while the experimental group was treated with different concentrations of TFDG(5,10μmol/L TFDG for 2 h)and then treated with high glucose for 24 h.The results showed that compared with model group,the cell viability and NO level of TFDG pretreatment group(5 and 10μmol/L)were significantly increased,the release level of lactate dehydrogenase(LDH)was significantly decreased,and the contents of intracellular reactive oxygen species(ROS)and lipid peroxide malondialdehyde(MDA)were significantly decreased,indicating that the damage of cell structure and function was reduced.Meanwhile,the results showed that the levels of inflammatory cytokines IL-6,IL-1βand TNF-αin TFDG pretreatment group were significantly decreased,and TFDG pretreatment could significantly reduce the inflammatory response of endothelial cells induced by high glucose.PartⅡ:The experimental model of T2DM rats was fed with high-sugar and high-fat diet plus intritoneal injection of streptozotocin(STZ),and continued to be fed with high-sugar and high-fat diet.Meanwhile,TFDG was administered with 5 and 10mg/kg_·d for 8 weeks.The results are as follows.Firstly,the observation results of abdominal aorta pathological section showed that compared with the model group,the pathological injury degree of artery vessels in TFDG dietary intervention group was improved.Secondly,the plasma level of NO was significantly increased and the level of MDA was significantly decreased in the intervention group.Finally,the levels of plasma inflammatory factors IL-6,IL-1βand TNF-αwere significantly decreased in the intervention group.Part Ⅲ:Western blot was used to observe the effects of TFDG on NLRP3inflammatory pathway in vascular endothelial cells under high glucose conditions.Results showed that compared with the model group,the expression levels of NLRP3,Cleaved caspase-1,Cleaved IL-1βand IL-1βin endothelial cells and aorta tissues in TFDG intervention group were significantly decreased.These results suggest that TFDG can effectively inhibit the activation of NLRP3/IL-1βinflammatory pathway induced by high glucose and reduce the inflammatory response of vascular endothelial cells.In conclusion,our results suggest that TFDG dietary intervention can effectively reduce vascular endothelial injury,maintain vascular endothelial function,and reduce oxidative injury and inflammatory response of endothelial cells in diabetic rats.The protective mechanism of TFDG may involve the inhibition of NLRP3/IL-1βinflammatory pathway.The detailed molecular mechanism remains to be further explored.